Ventilators

Impact Instrumentation 754M VT Plus: troubleshooting and error codes

The ServiceForge knowledge base holds 353 documented symptoms for the Impact Instrumentation 754M VT Plus, with 497 ranked causes, 726 diagnostic checks with test points and expected values, and 64 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

LCD Backlight does not work

LCD backlight does not illuminate or is very dim

Ranked causes

1. Backlight threshold set incorrectly (common)
2. Defective Backlight on Display PCB (occasional)
3. Defective light sensor (PC1) on Display PCB (occasional)
4. Connector to CPU PCB problem (occasional)
5. Defective LCD wiring (occasional)
6. LCD Backlight not plugged in (occasional)
7. Defective T2 on Power PCB (occasional)
8. Defective U8 (ULN2003) on Mtr. Drv PCB (occasional)
9. Through connection problem on Analog PCB (occasional)
10. Defective U6 (EPLD: XC7354) on CPU PCB (rare)

10 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Compressor Vt incorrect or cannot calibrate properly or changes erratically patient safety

Compressor tidal volume does not match set value, cannot be calibrated, or varies unpredictably

Ranked causes

1. VOR valves clogged or defective (occasional)
2. Flow Manifold leak or Exhaust Manifold leak (occasional)
3. Compressor leak or Backup valve activated (occasional)
4. Hose leaks with wire ties missing (occasional)
5. Defective U9 (AD7226) or defective TACH input on U1 (unknown)
6. EPLD outputs bad for compressor control (unknown)

First check

Measure delivered tidal volume with calibrated spirometer

Test point: Patient circuit outlet
Expected: Delivered volume matches set value within calibration tolerance

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Constant Vt alarm with external gas patient safety

Unit continuously triggers tidal volume alarm during external gas delivery

Ranked causes

1. VOR valves jamming; tank pressure sensor barb not cut short enough (occasional)
2. VOR valves clogged or defective (occasional)
3. Oscillation of O2 or Ext Air flow signals; wrong feedback capacitor (unknown)
4. Defective U1 or U2 (MC27L4) (unknown)
5. Other signal saturating A/D converter (unknown)
6. Defective channel on A/D converter of U1 (80C552-24) (unknown)

First check

Verify VOR valve operation

Test point: VOR valve inlet and outlet
Expected: Valve opens with gas supply and holds closed without supply

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

LCD does not work: lines on display or blank

LCD display shows lines or is completely blank

Ranked causes

1. CPU not running properly (occasional)
2. Defective U6 (EPLD: XC7354): LCDCS, LCDEN signals (rare)
3. Defective D3, D4 (1N4565) on CPU PCB (occasional)
4. Defective U14, Q1 on CPU PCB (occasional)
5. Defective U12 (VTEMP signal) on CPU PCB (occasional)
6. Saturated channel on U11, U12 inputs (>5V) on CPU PCB (occasional)

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Lung not inflating but gas flowing (all gas sources) patient safety

Gas flows to patient circuit but does not inflate patient lung (mechanical delivery failure)

Ranked causes

1. Defective exhaust valves or exhaust manifold (occasional)
2. Exhaust valves not plugged in, plugged in incorrectly, or wiring defective (occasional)
3. VOR valves clogged or defective (occasional)
4. Defective U6 (EPLD) exhaust valve control signals (unknown)
5. Anesthesia valve and patient circuit hoses unseated or missing (occasional)
6. Internal hoses not properly connected or leaking (occasional)

First check

Verify gas flow to lung

Test point: Patient circuit outlet with lung simulator
Expected: Gas flow pressurizes lung simulator during ventilation cycle

6 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Alarm LED does not work

Alarm LED does not illuminate when expected

Ranked causes

1. Q3 (2N3906) shorted on Display PCB (common)
2. D2 (LED) defective or installed backwards on Display PCB (occasional)
3. Q3 (2N3906) open on Display PCB (occasional)
4. Connector to CPU PCB: ALARM signal problem (occasional)

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery charger output is same as external input voltage high voltage

Battery charger fails to regulate or step down voltage; output equals input

Ranked causes

1. Unfused EXT+/BATT+ signal wired improperly (rare)
2. VEXTPWR signal bad (voltage divider R52, R53) (unknown)
3. VBATT signal bad (voltage divider R63, R64) (unknown)
4. Defective U7 (LM311) or voltage divider R13, R14 or D17 (unknown)

First check

Measure charger output voltage

Test point: Charger output
Expected: Regulated voltage lower than input

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Constant Vt alarm with compressor patient safety

Unit continuously triggers tidal volume alarm during compressor operation

Ranked causes

1. Defective U8 (ULN2003) (unknown)
2. Defective U4 (33039), U6 (4053), Q9, U2 (VSPEED), or U5 (33035) (unknown)
3. Boost Voltage Supply not working (U3) or drive transistors (unknown)
4. Overcurrent fault limiting motor speed (unknown)

First check

Measure compressor motor current

Test point: Motor current sense circuit
Expected: Normal current during operation, no overcurrent faults

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

No External Air or Oxygen Flow patient safety

External air or oxygen gas does not flow from tank or supply line to patient

Ranked causes

1. Valves not plugged in or wiring defective (common)
2. Bad U8 (ULN2003) (unknown)
3. Defective U6 (EPLD) exhaust valve control signals (unknown)
4. External tank valve not opened (common)

First check

Verify external tank valve is open

Test point: External tank supply valve
Expected: Valve fully open and tank pressure sufficient

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

One pushbutton activating without being pressed patient safety

Single pushbutton triggers action without being physically pressed

Ranked causes

1. Pushbutton switch shorted or shorted to ground (common)
2. Defective pushbutton switch (unknown)
3. CPU board connector issue (unknown)
4. SW10 switch installed backwards (rare)

First check

Verify pushbutton switch is not shorted

Test point: Affected pushbutton terminals
Expected: Open circuit when unpressed

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Only one upper row pushbutton not working

Single upper row pushbutton fails to respond when pressed

Ranked causes

1. Defective pushbutton switch (unknown)
2. Missing ground on pushbutton switch (unknown)
3. Connector to CPU board disconnected or defective (unknown)
4. Pushbutton switch shorted or shorted to ground (unknown)

First check

Test individual pushbutton switch continuity

Test point: Defective pushbutton terminals
Expected: Open when unpressed, continuity when pressed

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

RS232 cannot communicate for factory calibration mode

RS232 link unable to establish communication for factory calibration procedures

Ranked causes

1. Bad U1 MAX232 interface IC (unknown)
2. Defective U1 RXD or TXD pins (unknown)
3. Defective L1 or L2 inductor (unknown)
4. Connector to CPU board disconnected or defective (unknown)

First check

Test RS232 communication with calibration PC

Test point: RS232 connector CN3
Expected: Data received and acknowledged by calibration program

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

RS232 does not send out pressure and alarm data

RS232 serial communication fails to transmit pressure readings and alarm information

Ranked causes

1. External RS232 cable not plugged in (common)
2. External RS232 cable defective (occasional)
3. Defective U1 TXD output (unknown)
4. Bad U1 MAX232 interface IC (unknown)

First check

Verify RS232 cable connection

Test point: Connector CN3
Expected: Cable firmly seated and plugged in

4 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit does not turn on at all, no alarms when Mode Switch is activated high voltage

System does not power up and no System Failure LED or audible alarm occurs when Mode Switch is operated

Ranked causes

1. POWEROFF signal present or shorted component/IC pulling down +5V, +10V, +15V, or -15V supply (unknown)
2. Defective SW11 or defective Mode Switch (unknown)
3. Thru connection problem at SW11 or CPU Board connector (unknown)
4. Missing ground at SW11 (unknown)

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery charger has no output high voltage

Battery charging circuit does not produce output voltage

Ranked causes

1. Defective U2 (LM2577) or O2 not on in POWERON signal path or Lo-Bat shutdown circuit (unknown)
2. Shorted D2, D3, or D4 (unknown)
3. Any supply with shorted load pulling down all others (unknown)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Battery Voltage caution

Verify battery voltage is within nominal operating range and proper low battery and fail alarms occur at correct thresholds

Ranked causes

1. Battery voltage out of range (occasional)
2. Low battery alarm threshold incorrect (occasional)
3. Battery fail threshold incorrect (occasional)

First check

Measure battery voltage under load

Test point: Battery connector
Expected: 11.8V - 14.5V, 11.8V to 14.5V
Tools: DMM

2 more checks with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Compressor not running

Compressor motor fails to start or operate

Ranked causes

1. Compressor not plugged in, plugged in incorrectly, or hiring pinched (common)
2. Defective K2 power relay (not getting power to CN2 and Motor Drive PCB) (occasional)
3. Compressor defective (rare)

First check

Verify compressor power connector

Test point: Compressor power connector
Expected: Connector fully seated with continuity on all pins

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Compressor not running properly (too slow)

Compressor motor operates but runs at reduced speed below normal operation

Ranked causes

1. Bad U4 (33039), U6 (4053), Q9 not on, U2 VSPEED problem, or U5 (33035) (unknown)
2. Boost Voltage Supply not working (U3) or drive transistor problem (unknown)
3. Overcurrent fault limiting motor speed (unknown)

First check

Measure motor speed signal (VCOMPRESSOR)

Test point: VCOMPRESSOR on Motor Drive PCB
Expected: Speed voltage should match VSPEED command

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Factory calibration cannot calibrate one of the sections

Calibration procedure fails to adjust or verify one particular sensor or control section

Ranked causes

1. Respective signal not valid: dead/open/saturated (unknown)
2. Hardware calibration incorrect (unknown)
3. Problem with transducer signal (unknown)

First check

Verify signal presence at problem section input

Test point: Transducer or amplifier output for affected section
Expected: Valid signal within operating range

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Factory calibration cannot protect/unprotect EEPROM

Unable to toggle EEPROM write protection during factory calibration

Ranked causes

1. Bad U1 MAX232 interface IC (unknown)
2. Defective L1 or L2 inductor (unknown)
3. Connector to CPU board disconnected or defective (unknown)

First check

Test RS232 protection command transmission

Test point: RS232 interface
Expected: Protection command received and acknowledged

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Factory calibration cannot save (F4)

Calibration data cannot be stored using F4 save function during factory calibration

Ranked causes

1. Defective U5 EEPROM (NMC9366) (unknown)
2. Wrong U5 EEPROM installed (NMC9366 instead of NMCS9366) (rare)
3. Problem at J3 connector (unknown)

First check

Verify EEPROM part number

Test point: U5 component
Expected: NMCS9366 installed

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Input voltage regulator fails high voltage

Input voltage regulation circuit does not function properly

Ranked causes

1. External power source starving system for current (unknown)
2. Shorted C1 or VR1 (unknown)
3. Shorted C2 on Filter PCB at power jack (unknown)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low External Air or Oxygen Flow patient safety

External air or oxygen gas flow is reduced but present

Ranked causes

1. Transducers not connected, defective, or wiring problem (occasional)
2. Through Connection problem (unknown)
3. EPLD output signals bad (U6 pins for air/O2) (unknown)

First check

Measure external gas flow signal

Test point: External air/oxygen flow transducer output
Expected: Signal present and proportional to flow rate

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low external power does not switch to battery or switches at wrong voltage patient safety

Unit fails to switch from external to battery power when external power is low, or switches at incorrect threshold

Ranked causes

1. Defective U7 (LM311) (unknown)
2. Problem with voltage divider R13, R14 or D17 reference (unknown)
3. Through Connection Problem (unknown)

First check

Measure external power switching threshold

Test point: U7 output and external power input
Expected: Switching occurs at specified threshold voltage

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Manual breathing pushbutton does not activate patient safety

Manual breathing pushbutton fails to respond when pressed

Ranked causes

1. Defective pushbutton switch (unknown)
2. Connector to CPU board disconnected or defective (unknown)
3. Pushbutton switch shorted or shorted to ground (unknown)

First check

Test Manual breathing pushbutton continuity

Test point: Manual breathing pushbutton terminals
Expected: Open when unpressed, continuity when pressed

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Motor speed control malfunction

Motor does not respond to speed control signals or control signals missing

Ranked causes

1. Shorted power wiring in wiring harness or at fuseholder or short between pins in CN2/CN5 (unknown)
2. PWRCTL signal not low (unknown)
3. Q10 (IRF9Z34) not turned on or defective (unknown)

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

No 40 cmH2O overpressure indication (no buzzer or System Failure LED) patient safety

Overpressure alarm (40 cmH2O) does not trigger LED or buzzer

Ranked causes

1. Defective Q1, Q2 (2N222) or R60, R61 on Analog PCB (common)
2. Problem with Backup Pressure Relief circuit (occasional)
3. BUAKPRESSUREOK signal does not switch low at 40 cmH2O (occasional)

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

No System Failure alarm with fuses removed or no +15V supply patient safety

Unit fails to indicate system failure when fuses are removed or +15V supply is absent

Ranked causes

1. Open D26 or problem with P.S. Monitor circuit (unknown)
2. Problem with Fuse Monitor circuit (unknown)
3. Defective U1 (LM3578) (unknown)

First check

Remove fuse and verify system failure alarm

Test point: Fuse monitor circuit and alarm output
Expected: System failure alarm activates when fuse is removed

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

System fail LED comes on patient safety

LED illuminates during high airway pressure safety shutdown test (Failure Code 5) or low airway pressure test (Failure Code 6)

Ranked causes

1. Airway pressure exceeds 40 cmH2O for more than 4 seconds (Failure Code 5) (common)
2. Airway pressure reaches +100 cmH2O during high pressure test (Failure Code 5 continued) (common)
3. Low airway pressure condition (Failure Code 6) (occasional)

First check

Pressurize test syringe to airway pressure above 40 cmH2O

Test point: Airway transducer
Expected: Above 40 cmH2O, >40
Tools: Syringe with hose, test lung

4 more checks with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

System Failure LED and Buzzer on steady

Both System Failure LED and audible alarm sound continuously

Ranked causes

1. D10 backwards or open on Display PCB (common)
2. Problem at Q4 on Display PCB (occasional)
3. No FAILURE signal from CPU PCB (occasional)

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

System Failure LED on steady

System Failure LED illuminates continuously

Ranked causes

1. D1 backwards or open on Display PCB (common)
2. Bad ground on cathode side of D1 (occasional)
3. PCB trace problem (occasional)

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Total Flow Backup alarm patient safety

Alarm triggered, often accompanied by flow sensing issues or tidal volume inaccuracies

Ranked causes

1. Clogged or dirty flow sensing screen (common)
2. Defective Mix Flow Transducer (occasional)
3. Hardware calibration issue (occasional)

First check

Inspect flow sensing screen

Test point: Gas Out To Patient fitting
Expected: Screen clean, no visible dust or debris when held to light

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Total Flow Backup alarm triggered

Alarm activates during operation, potentially indicating flow measurement issue or intake contamination

Ranked causes

1. Dust and debris accumulation on flow sensing screen (common)
2. Defective Mix Flow Transducer (occasional)
3. Hardware calibration issue (occasional)

First check

Inspect flow sensing screen for dust and debris accumulation

Test point: Flow sensing screen under Gas Out To Patient fitting
Expected: Clean screen visible when held to light source

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit does not control modes properly

Mode Switch does not select or transition between operating modes correctly

Ranked causes

1. Defective SW11 switch (unknown)
2. Connector to CPU board disconnected or defective (unknown)
3. Missing ground at SW11 (unknown)

First check

Test SW11 mode selection contacts

Test point: SW11 switch
Expected: Correct continuity pattern for each mode position

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit does not turn off when in off position

Mode Switch control fails to power down the unit despite being set to off position

Ranked causes

1. Defective SW11 switch (unknown)
2. Connector to CPU board disconnected or defective (unknown)
3. Missing ground at SW11 (unknown)

First check

Verify SW11 switch continuity

Test point: SW11 switch
Expected: Continuity when switch in on position, open when off

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit does not turn on at all, no alarms

Mode Switch fails to power up unit; no LED, display, or alarm activity

Ranked causes

1. Defective SW11 switch (unknown)
2. Connector to CPU board disconnected or defective (unknown)
3. Missing ground at SW11 (unknown)

First check

Verify SW11 switch operation

Test point: SW11 switch
Expected: Open circuit when off, continuity when on

3 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit fuse blows when battery power applied high voltage

Fuse is destroyed immediately upon connecting battery power

Ranked causes

1. Short between pins 6 & 7 on CN5 (Power Connector) (unknown)
2. Transistor Q1-Q6 not installed properly with tabs shorting to each other (unknown)
3. Thru connection problem (unknown)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit fuse blows when compressor activated high voltage

Fuse is destroyed when compressor motor is turned on or starts running

Ranked causes

1. Defective compressor (unknown)
2. Short in motor winding (winding to winding or to ground) or short to ground on standoff (unknown)
3. Short to ground in Battery Charger or short in power wiring at fuseholder (unknown)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit fuse blows when external power first applied high voltage

Fuse is destroyed immediately upon connecting external power

Ranked causes

1. Open D25 (unknown)
2. Thru connection problem to AC power supply (unknown)
3. Input voltage too high (unknown)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Unit is completely dead, battery plugged in and no external power high voltage

Unit does not respond with battery installed and no external power connected

Ranked causes

1. AC power not live (unknown)
2. Battery below 10V (unknown)
3. Thru connection problem (unknown)

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Alarm LED does not respond correctly to mute

After pressing Mute/Cancel during a Disconnect alarm, the alarm LED should change from blinking to solid on for 30 seconds, then resume blinking. After canceling an External Power Fail alarm, the LED should turn off completely.

Ranked causes

1. Mute/Cancel button not functioning properly (unknown)
2. LED circuit malfunction (unknown)

First check

Generate Disconnect alarm and press Mute/Cancel button

Test point: Alarm LED
Expected: LED changes from blinking to solid on

3 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Alarm LED does not respond to alarm condition

Alarm LED fails to blink when alarm generated or does not respond to Mute button; does not turn off when fault corrected

Ranked causes

1. Alarm LED circuit defective (occasional)
2. Disconnect alarm not being generated (rare)

First check

Generate Disconnect alarm

Test point: Patient circuit connection
Expected: Alarm audibly sounds or alarm LED blinks

3 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Audible alarm comes on continuously patient safety

Continuous audible alarm sounds during ventilator operation when airway pressure exceeds safety threshold

Ranked causes

1. Airway pressure exceeds 40 cmH2O for 4 seconds (Safety Shutdown triggered) (common)
2. Exhaust valve failure (Failure Code 5) (occasional)

First check

Set ventilator to A/C mode with specified parameters

Test point: Mode setting
Expected: Mode = A/C; Rate = 15 BPM; I time = 1.0 sec; Vt = 500 ml; FIO2 = 21%

3 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery voltage out of acceptable range patient safety

Measured battery voltage under load is outside specified operating range

Ranked causes

1. Battery discharged or failing (common)
2. Charging circuit malfunction (occasional)

First check

Measure battery voltage under load

Test point: battery connector cable
Expected: 11.8V - 14.5V, 11.8V - 14.5V
Tools: DMM

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Battery voltage out of specification patient safety

Measured battery voltage under load does not fall within acceptable operating range

Ranked causes

1. Battery degraded or failing (common)
2. Charger malfunction or external power supply failure (occasional)

First check

Measure battery voltage under load

Test point: Battery connector cable
Expected: 11.8V - 14.5V, 11.8–14.5V
Tools: Voltmeter

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Buzzer does not work

Buzzer does not sound when expected

Ranked causes

1. Defective U2 or Q2 (TLC227212NZ22) on Display PCB (common)
2. Connector to CPU PCB problem (occasional)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Buzzer works for either Operating Alarms only or PB indication only

Buzzer activates for only one type of alarm, not both operating alarms and push-button

Ranked causes

1. Problem with R12 or R13 (10W24K) on CPU PCB (occasional)
2. Defective U6 (EPLD: XC7354): PIEZOL or PIEZOH signal (rare)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Buzzer works for Power problems only

Buzzer activates only on power-related faults, not other alarms

Ranked causes

1. Problem with Q4, D8, D10, R9, R10, R16 on Display PCB (occasional)
2. Connector to CPU PCB problem (occasional)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: External Power Low caution

Verify external power low alarm triggers at correct voltage threshold and unit shuts down at fail threshold

Ranked causes

1. External Power Low alarm threshold incorrect (occasional)
2. External power fail shutdown threshold incorrect (occasional)

First check

Verify External Power Low alarm occurs

Test point: External power voltage; AMC display; PIC Line 1
Expected: Alarm at 10.5V - 11.1V; AMC shows EXTERNAL POWER LOW; PIC shows EXT PWR LOW, 10.5V to 11.1V
Tools: Variable power source, DMM

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Cancel function does not stop External Power Fail alarm patient safety

Pressing Cancel button does not stop audible alarm or turn off alarm LED after external power failure

Ranked causes

1. Cancel button not responding to power fail condition (rare)
2. Alarm management circuit failure (rare)

First check

Disconnect external power

Test point: AC power inlet
Expected: External Power Fail alarm generated

3 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Charge LED does not illuminate

Charge LED fails to light during charging with external power supply and battery disconnected

Ranked causes

1. Power supply not connected or faulty connection (common)
2. Charge LED circuit defect or LED failure (occasional)

First check

Verify external power supply is connected

Test point: Power supply connector
Expected: External power supply connected and powered on

2 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Charge LED does not work

Charge LED does not illuminate when expected

Ranked causes

1. Defective Q5 on Display PCB (common)
2. Defective U2 on Display PCB (occasional)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Factory calibration saved OK until EEPROM protected

Calibration saves successfully but fails immediately upon EEPROM protection

Ranked causes

1. Defective U5 EEPROM (NMCS9366) (unknown)
2. Wrong U5 EEPROM installed (NMC9366 instead of NMCS9366) (rare)

First check

Verify correct EEPROM part number installed

Test point: U5 component
Expected: NMCS9366 (not NMC9366)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Low battery shutdown at wrong voltage patient safety

Unit shuts down from battery power at incorrect threshold voltage

Ranked causes

1. Q2 not shutting off OK or shorted; voltage divider R4, R5 problem (unknown)
2. Defective U8 (LM311) or voltage divider R18, R19 or D18 (unknown)

First check

Measure battery shutdown threshold

Test point: U8 comparator input and output
Expected: Shutdown occurs at specified battery voltage

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

Mute function does not silence alarm for 30 seconds patient safety

Pressing Mute/Cancel button does not silence audible alarm or alarm LED does not change state

Ranked causes

1. Mute/Cancel button not functioning (rare)
2. Alarm circuit malfunction (rare)

First check

Generate Disconnect alarm

Test point: Patient circuit
Expected: Disconnect alarm active

4 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Mute/Cancel button not silencing alarm

Pressing Mute/Cancel button does not temporarily silence audible alarm for 30 seconds

Ranked causes

1. Mute/Cancel button malfunction (occasional)
2. Alarm LED not responding to Mute (occasional)

First check

Verify audible alarm mutes for 30 seconds

Test point: Audible alarm speaker
Expected: Alarm mutes; resumes after 30 seconds

2 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

No blown fuse indication on LCD with one power source functional caution

LCD display fails to indicate blown fuse condition even when one power source is present

Ranked causes

1. Through Connection Problem (FAILURE signal) (unknown)
2. Defective U12 (4051) or A/D channel on U1 (unknown)

First check

Monitor FAILURE signal with fuse removed

Test point: FAILURE signal from power circuits
Expected: Signal present when fuse is open

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

No low battery alarm patient safety

Unit fails to generate alarm when battery voltage is low

Ranked causes

1. Q2 not shutting off OK or shorted; voltage divider R4, R5 problem (unknown)
2. Defective U8 (LM311) or voltage divider R18, R19 or D18 (unknown)

First check

Discharge battery and verify low battery alarm

Test point: Battery input and alarm output
Expected: Alarm indication when battery voltage below threshold

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

No low external power alarm patient safety

Unit fails to generate alarm when external power supply voltage is low

Ranked causes

1. Defective U7 (LM311) or voltage divider R13, R14 or D17 (unknown)
2. Problem with voltage divider R13, R14 or D17 reference (unknown)

First check

Apply low external power and verify alarm

Test point: Unit external power input and alarm output
Expected: Alarm indication when external power below threshold

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

No System Failure indication (no buzzer or System Failure LED)

Neither System Failure LED nor audible buzzer activates when expected

Ranked causes

1. Shorted Q2 (2N3906) on Display PCB (common)
2. CPURUN signal shorted to ground (occasional)

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

More symptoms

Potentiometer does not operate over full range
Power supply shutdown or fuse protection activation
RT-200 does not communicate with 754 computer
System Fail LED does not activate on external power loss
System Failure LED and Audible Alarm steady
System Failure LED does not work
Unit blows Battery fuse only
Unit blows both fuses
Unit blows Exit Power fuse only
Unit does not hold PEEP
Unit does not turn off
Unit fuse blows when battery charger output connected
Unit is completely dead, external power and/or battery connected and no output
Unit resets/shuts down when compressor starts
Ventilator Failure Code 2 not generated on loss of gas supply
Ventilator Failure Code 2 not occurring
40 cmH2O safety shutdown not functioning
Alarm cancel clears all alarm indicators
Alarm cancel function not working
Alarm cancels when rate increased
Alarm cancels when rate increased above threshold
Alarm does not cancel on external power loss
Alarm does not cancel when expected
Alarm does not mute or remute correctly
Alarm LED and audible alarm not clearing on Mute/Cancel
Alarm LED and audible alarm not turning off after Mute/Cancel
Alarm LED behavior during mute
Alarm LED does not blink on alarm condition
Alarm LED does not change state when Mute/Cancel button pressed
Alarm LED does not go solid when Mute/Cancel pressed
Alarm LED does not respond to disconnect alarm
Alarm LED does not transition from blinking to solid during mute
Alarm LED not responding to alarm condition
Alarm LED on steady
Alarm LED or audible alarm does not silence after Mute/Cancel button press
Alarm LED or audible alarm does not turn off after Mute/Cancel
Alarm Message Center (AMC) does not clear on Cancel
Alarm Message Center continues displaying alarm after disconnect condition fixed
Alarm Message Center does not clear when Mute/Cancel cancels alarm
Alarm Message Center does not display correctly during mute
Alarm message display during mute
Alarm mute function not working
Alarm Mute/Cancel button inoperative
Alarms cancel at lower Vt setting
Alarms cancel when condition resolved
Alarms cancel when Vt decreased to 500 ml
Alarms cancel when Vt decreased to acceptable range
Alarms cancel when Vt decreased to safe level
Alarms cancel when Vt decreases
Alarms cancel when Vt setting normalized
Alarms clear on Vt decrease
Alarms clear when Vt setting normalized
All four upper row pushbuttons not working
AMC message does not remain after Mute/Cancel
Apnea detection rate out of specification
Apnea rate backup outside specification
Audible alarm does not mute when Mute/Cancel button pressed
Audible alarm does not stop when expected
Audible alarm mute duration incorrect
Audible alarm mute function
Autocal valve not returning to baseline
Backup ventilator mode not functioning
Bar graph display missing lines or pixels
Battery fail alarm not activating or shutdown not occurring
Battery fail alarm not triggering at correct voltage
Battery fail alarm not triggering at shutdown threshold
Battery fail shutdown does not occur at correct voltage
Battery fail shutdown not occurring at threshold
Battery voltage out of range
Battery voltage out of range during operation
Battery voltage out of spec under load
Battery voltage out of specification on load
Battery voltage outside operational range
Buzzer on steady
Buzzer works for Operating Alarms and PB indication only
Calibration abort alarm on mode switch during calibration
Calibration abort during mode switch
Calibration mode abort alarm triggered
Calibration mode not functioning
Calibration: Airway pressure baseline
Calibration: Apnea Alarm in A/C and SIMV
Calibration: Apnea Alarm in CPAP
Calibration: Autocal valve pressure baseline
Calibration: Backup Ventilation Test
Calibration: Battery Run Test
Calibration: Charger Voltage
Calibration: Computer calibration setup and verification
Calibration: Default 1:2 I:E Ratio
Calibration: Demo Mode
Calibration: External Power Low alarm threshold
Calibration: High Pressure Alarm
Calibration: I Time Truncated To 3-Sec Alarm
Calibration: Inspiration time setting verification
Calibration: Inverse I:E Alarm
Calibration: Low Pressure Alarm
Calibration: Pressure Plateau
Calibration: Pressure Settings Alarm
Calibration: Pressure transducer baseline verification
Calibration: Real Time Clock reset
Calibration: System shutdown at low voltage threshold
Calibration: Tidal volume and gas delivery
Calibration: Unit pressure sensor
Cancel alarm function clears all alarm indicators
Cancel button not clearing alarm
Charge LED not illuminating
Charge LED on steady
Charger output voltage out of range
Charger output voltage out of spec
Charger output voltage out of specification
Charger voltage out of range
Charger voltage out of specification
Charger voltage output incorrect
Charger voltage outside specification
Compressor alarm not activating during mode switching
Compressor motor failure
Connector ridge modification
CPAP demand flow malfunction
CPAP I time outside specification
CPAP PIP relief pressure outside specification
CPAP spontaneous flow insufficient
Default 1:2 I:E ratio not achieved
Default 1:2 I:E ratio not verified
Default 1:2 I:E Ratio verification
Default I:E ratio incorrect
Default I:E ratio not 1:2
Default I:E ratio not set correctly
Digital bar graph display is incomplete
Digital bar graph does not reach 100 cmH2O
Disconnect alarm does not deactivate after condition is fixed
Disconnect alarm muting
Disconnect alarm not muting
Exhaust valve opens and stays open
External air supply not toggling or pressure threshold alarm not activating
External Power Fail alarm canceling
External Power Fail alarm does not occur
External Power Fail alarm not occurring
External power low/fail alarm outside specification
Failure Code 5 (Exhaust Valve Failure) alarm during high pressure test
Failure Code 5 alarm with high pressure
Failure Code 5 not displayed on unit shutdown
Failure Code 5 occurs with high airway pressure
Failure Code 5 triggered
Failure Code 5 triggered during high airway pressure test
Failure Code 5 triggered during high pressure test
Failure Code 5 triggered during safety shutdown test
Failure Code 6 (Low Pressure Condition)
Failure Code 6 triggered
Final Inspection
FIO2 and O2 Low/Fail alarm not activating
FIO2 reading out of specification
FiO2 reading outside acceptable range
Fuse check procedure and failure indication
I time setting outside specification
I Time Truncated alarm cancels at higher rate
I Time Truncated alarm cancels when rate increased
I Time Truncated alarm clears on rate increase
I Time Truncated alarm clears when rate increased
I Time Truncated To 3-Sec alarm cancels at 7 BPM
I Time Truncated To 3-Sec alarm clears when rate increased
I Time Truncated To 3-Sec alarm does not cancel
I Time Truncated To 3-Sec alarm occurs
I Time Truncated To 3-Sec alarm occurs at 6 BPM
I Time Truncated To 3-Sec alarm occurs at low rate
I:E ratio not at default 1:2
Inspiration time 2.0 seconds out of tolerance
Inspiration time 3.0 seconds out of tolerance
Inspiration time control calibration
Inspiration time does not measure 0.5 seconds
Inspiration time does not measure 2.0 seconds
Inspiration time does not measure 3.0 seconds
Inspiration time measurement out of tolerance
Inspiration time measures incorrectly
Inspiration time not measuring correctly
Inspiration time not within specification
Inspiration time not within tolerance
Inspiration time out of spec
Inverse I:E alarm occurs
Inverse I:E alarm occurs at 1.1 sec I time with 30 BPM
Inverse I:E alarm occurs at high I time setting
LCD contrast problem: contrast too dark (blue) or too faint
LCD inspiration/exhalation indicator verification
LCD power information display verification
LCD visual indicator verification: Inspiration/Exhalation display
LCD visual indicator verification: Vmin display
LCD Vmin display verification
Low battery alarm does not display
Low Battery Alarm does not occur at correct voltage
Low battery alarm does not trigger
Low battery alarm does not trigger at correct threshold
Low Battery Alarm does not trigger at correct voltage
Low battery alarm not activating
Low battery alarm not triggering at correct voltage
Low battery alarm not triggering at specified threshold
Low battery alarm not triggering correctly
Manual trigger does not deliver gas flow
Manual Trigger does not function correctly
Manual trigger does not stop gas flow at pressure limit
Manual trigger does not stop gas flow at pressure threshold
Manual Trigger gas flow does not stop at correct pressure
Manual trigger in backup ventilator not responding
Manual trigger not functioning in backup ventilator
Manual trigger not responding in backup ventilator
Mean airway pressure display incorrect
Mean airway pressure display not reading correctly
Memory check failure (Failure Code 4)
Mute alarm function operates correctly
Mute function does not suppress alarm for 30 seconds
Mute silences I Time Truncated alarm but message remains
Mute/Cancel button - alarm cancellation function
Mute/Cancel button - alarm muting function
Mute/Cancel button does not mute alarm
Mute/Cancel button does not mute audible alarm
Mute/Cancel button silences alarm
Mute/Cancel control alarm canceling function
Mute/Cancel control alarm muting function
Mute/Cancel does not cancel External Power Fail alarm
Mute/Cancel pushbutton does not activate
Peak airway pressure display incorrect
Peak Airway Pressure display missing lines or pixels
Peak airway pressure display not reading correctly
PEEP control verification failed
PEEP setting outside acceptable range
PIP relief does not occur at correct pressure
PIP relief does not trigger at correct pressure
PIP relief in backup ventilator incorrect
PIP relief in backup ventilator not functioning
PIP relief not functioning in backup ventilator
PIP relief not occurring at correct pressure
Pip relief not occurring at correct pressure in backup ventilator
Rate setting outside specification
Real Time Clock Reset
Real-time clock reading incorrect
RTC battery voltage low
Safety Shutdown at 40 cmH2O pressure
Safety shutdown triggered
Spontaneous flow rate out of specification
Spontaneous flow rate outside specification
System does not shut down at Battery Fail threshold
System does not shut down at Battery Fail voltage
System Fail LED and alarm not triggered on external power loss
System Fail LED not responding to power loss
System failure LED does not illuminate during battery fail
System Failure LED works for CPURUN problems only
System Failure LED works for Power Supply problems only
System shuts down unexpectedly
Test lung circuit not set up correctly for manual trigger verification
Test lung circuit not set up correctly for Pip relief verification
Tidal volume out of specification
Tidal volume outside acceptable range
Total Flow Backup Alarm does not occur
Total Flow Backup Alarm does not silence after Mute/Cancel
Total Flow Backup alarm not activating
Total Flow Backup Alarm not occurring
Total Flow Backup Alarm not triggered
Total Flow Backup Alarm occurs
Total Flow Backup Alarm triggers
Unit does not shut down at battery fail threshold
Unit does not shut down at high airway pressure
Unit does not shut down at low battery voltage
Unit does not shut down when all gas supplies disconnected
Unit gives Failure Code 2 (No Gas, COMP) alarm
Unit should shut down
Unit should shut down after gas supply loss
Ventilator fails to power up on external power
Ventilator Failure Code 2 (No Gas, COMP)
Ventilator Failure Code 2 (No Gas, COMP) does not occur
Ventilator Failure Code 2 alarm
Ventilator Failure Code 2 alarm (No Gas, COMP)
Ventilator Failure Code 2 does not occur
Ventilator Failure Code 2 not generated
Ventilator Failure Code 2 triggers
Ventilator Failure Code 5 (Exhaust Valve Failure)
Ventilator Failure Code 6 (Excessive Negative Pressure)
Verify normal calibration completion
Vt alarm cancels at 500 ml setting
Vt alarm clears
Vt alarm displaces previous alarm on AMC
Vt alarm displaces previous alarm on display
Vt alarm displaces Settings alarm on display
Vt alarm displaces Vt Settings alarm on AMC
Vt alarm not activating or not displacing previous alarm
Vt alarm occurs
Vt alarm occurs at 1150 ml setting
Vt alarm occurs at higher setting
Vt alarm occurs at higher threshold
Vt alarm occurs on further increase
Vt alarm occurs when setting increased
Vt alarm overrides Vt Settings alarm
Vt alarm overrides Vt Settings alarm on display
Vt alarm replaces Settings alarm on display
Vt alarms cancel
Vt Settings alarm not activating or canceling
Vt Settings alarm occurs

293 more symptoms with ranked causes and checks are in ServiceForge. Connect ServiceForge to your AI

Error codes

Code	Meaning	Trigger	Severity
`1 (Transducer Cal Fail)`	Pressure transducer calibration verification failed	Ventilator detects transducer output outside expected range during self-test or operation	error
`2 (No Gas, Comp)`	No gas supply or compressor failure detected	Ventilator unable to detect adequate gas flow or pressure from supply or compressor	critical
`3 (Excessive Airway Pressure)`	Airway pressure exceeds safe limit	Ventilator pressure transducer reads above preset safety threshold for more than specified duration	critical
`4 (Memory Check) / (Excessive Airway Pressure)`	Internal memory error or excessive airway pressure depending on firmware version	Ventilator detects memory corruption during self-test or pressure exceeds limit	error
`5 (Exhalation Valve Failure) / (Memory Check)`	Exhalation valve malfunction or memory integrity error depending on firmware version	Exhalation valve fails to open/close properly or memory checksum failure on startup	error
`6 (Exhaust Valve Fail) / (Excessive Negative Pressure)`	Exhaust valve malfunction or excessive negative pressure detection	Exhaust valve fails to function or ventilator detects excessive negative pressure in circuit	error
`7 (Excessive Negative Pressure) / (Run-Time Cal Fail)`	Excessive negative pressure detected or runtime calibration failure	Pressure transducer reads below negative threshold or runtime calibration check fails	warning
`Calibration Abort Alarm`	Calibration was aborted or interrupted	Mode control switched away from CAL mode before calibration completed	warning
`CHK EXT FUSE`	External power fuse (front fuse) failure detected	Occurs when front fuse is removed or has opened	error
`CHK FUSE`	Battery fuse (rear fuse) failure detected	Occurs when rear fuse is removed or has opened	error
`Code 1`	Transducer calibration failure (Ver 1.83X)	Pressure transducer unable to calibrate or sensor malfunction detected	critical
`Code 2`	No Gas, Comp	Compressor fails to produce adequate gas output	critical
`Code 3`	Excessive total flow backup or excessive airway pressure (Ver 1.83X / 1.85X)	Flow or pressure exceeds safe limits during ventilation	critical
`Code 4`	Memory Check	Memory integrity check fails (Ver 1.85X)	error
`Code 4`	Memory error or excessive airway pressure (Ver 1.83X / 1.85X)	EEPROM checksum failure or sustained high pressure condition	warning
`Code 5`	Memory Check	System memory integrity check fails (Ver 1.83X)	error
`Code 5`	Memory check failure (Ver. 1.83X) or Exhalation valve failure (Ver. 1.85X)	EEPROM self-check fails or exhalation valve not operating properly	error
`Code 6`	Exhaust valve failure (Ver. 1.83X) or Excessive negative pressure (Ver. 1.85X)	Exhaust valve does not open or inhalation effort creates excessive negative pressure	error
`Code 6`	Exhaust Valve Fail	Exhaust/exhalation valve does not open or close properly (Ver 1.83X)	error
`Code 7`	Run-Time Cal Fail	Calibration check fails during operation (Ver 1.85X)	error
`Code 7`	Excessive negative pressure (Ver. 1.83X) or Run-time calibration failure (Ver. 1.85X)	Patient inspiratory effort exceeds safe negative pressure or runtime cal procedure fails	warning
`COMP alarm`	Compressor mode switching conflict or compressor failure during switching	Occurs when unit switches between external air and compressor mode too rapidly or compressor cannot start	warning
`Disconnect`	Patient circuit is disconnected or unsecured	Patient circuit connector becomes disconnected during ventilation	critical
`Disconnect`	Disconnect alarm triggered during testing	Patient circuit disconnected from ventilator	warning
`Disconnect alarm`	Patient circuit or external connection disconnected	Loss of connection to patient circuit or external component	warning
`External Air Low/Fail`	External air supply pressure below threshold or failed	Occurs when external air supply pressure drops below 35 PSI	warning
`External Power Fail`	External power supply is absent or below minimum voltage	Top fuse removed or external power supply disconnected/unpowered	error
`External Power Fail alarm`	External power source disconnected or failed	Loss of external power supply	error
`EXTERNAL POWER LOW`	External power voltage has dropped to the warning threshold	External power voltage drops to 10.5–11.1 V range	warning
`EXT PWR FAIL`	External power supply disconnected or failed	Occurs when external AC power is not present	warning
`Failure Code 1`	Self Check failure during startup	Self-check test fails when unit powers on	critical
`Failure Code 2`	No Gas, COMP - compressor gas supply lost or unavailable	Both external air and oxygen supplies disconnected during operation	critical
`Failure Code 2`	No Gas, COMP condition	Both external air and oxygen supplies disconnected or unavailable after COMP alarm	critical
`Failure Code 2 (No Gas, COMP)`	No gas supply available and compressor failure detected during startup	Both external air and oxygen supplies disconnected after COMP alarm generation	critical
`Failure Code 2 (No Gas, COMP)`	Ventilator failure due to no gas supply with compressor alarm	Both external air and oxygen supplies disconnected or depleted after COMP alarm activation	critical
`Failure Code 2 (No Gas, COMP)`	Unit has shut down due to loss of both compressed air and oxygen supply during operation	Both external air and oxygen supplies disconnected simultaneously	critical
`Failure Code 3`	Excessive Airway Pressure sensed during startup	Airway pressure exceeds safe threshold during ventilator initialization	critical
`Failure Code 4`	Memory check failure	Memory check fails during system operation	error
`Failure Code 5`	Exhaust Valve Failure	Airway pressure remains above 40 cmH2O for 4 seconds during safety shutdown test; further pressure increase to +100 cmH2O for 2 seconds	critical
`Failure Code 6`	Low airway pressure condition	Airway pressure drops to -10 cmH2O or below	error
`Failure Code 6`	Excessive Negative Pressure	Airway pressure drops to -10 cmH2O for 1.5 seconds or more	critical
`Failure Code 6`	Negative pressure or sensor failure (incomplete in source text)	Airway pressure decreases to -10 cmH2O	error
`Failure Code 7`	Run-Time Transducer Calibration failure	Transducer calibration check fails during operation	critical
`FIO2 alarm`	Oxygen concentration cannot reach set point	Occurs when oxygen supply is insufficient to deliver set FIO2	warning
`Inverse I:E`	Inverse I:E ratio detected	Inspiratory time increased to 1.1 seconds at 30 BPM rate	warning
`Inverse I:E`	Inspiratory time exceeds or equals expiratory time creating inverted breath ratio	I time setting increased to equal or exceed expiratory time (e.g., I time 1.1 sec at 30 BPM with 1:2 ratio)	warning
`Inverse I:E alarm`	Inspiratory time exceeds expiratory time	Inspiratory time set to 1.1 seconds at 30 BPM rate	warning
`I Time Truncated To 3-Sec`	I time would exceed 3 seconds; system limits it	Rate set to 6 BPM with 1:2 I:E ratio default setting	warning
`I Time Truncated To 3-Sec`	Inspiratory time automatically reduced to 3 seconds due to respiratory rate constraints	Respiratory rate set too low (6 BPM) with default I:E ratio causing I time truncation to avoid excessive cycle time	warning
`I Time Truncated To 3-Sec alarm`	I time cannot be delivered as set due to respiratory rate; system limits to 3 seconds maximum	I time setting incompatible with rate (6 BPM with 1:2 I:E ratio)	warning
`I Time Truncated to 3-Sec alarm`	Inspiratory time would exceed breath cycle at current respiratory rate	Rate set to 6 BPM or lower with default I:E ratio	warning
`O2 Low/Fail`	Oxygen supply pressure below threshold or failed	Occurs when oxygen tank pressure drops below 35 PSI	warning
`Total Flow Backup alarm`	Airway flow drops below expected level during compressor operation	Occurs after 4-5 breaths when actual Vt is less than half the set Vt	warning
`Total Flow Backup Alarm`	Insufficient gas flow detected	Actual tidal volume falls below half of set tidal volume	error
`Total Flow Backup Alarm`	Actual delivered tidal volume has fallen below half of the set tidal volume due to airway obstruction or system failure	Compressor inlet obstruction reduces actual tidal volume to less than 50% of set value for 4-5 breaths	warning
`Vt`	Tidal volume alarm on further threshold breach	Vt set to 1150 ml or higher	warning
`Vt`	Tidal volume alarm indicating critical setting limit exceeded	Vt setting increased to 1150 ml (beyond upper safety limit)	error
`Vt`	Tidal volume delivery alarm	Delivered tidal volume falls outside alarm limits when Vt setting increased further (e.g., to 1150 ml)	error
`Vt alarm`	Vt reading deviates significantly from setting	Vt setting at 1150 ml or measurement exceeds threshold	warning
`Vt alarm`	Delivered tidal volume does not match set tidal volume	Occurs when Vt is set to 1150 ml or higher	warning
`Vt alarm`	Tidal volume measurement exceeds alarm limit	Measured tidal volume exceeds threshold at 1150 ml setting	warning
`Vt Settings`	Tidal volume setting is outside acceptable parameters	Tidal volume set to value exceeding alarm threshold (e.g., 1050 ml)	warning
`Vt Settings`	Vt setting outside acceptable range	Vt setting changed to 1050 ml or higher	warning
`Vt Settings alarm`	Tidal volume setting exceeds safe operating range	Tidal volume setting changed to 1050 ml or higher	warning

Likely causes and actions for each code are in ServiceForge. Connect ServiceForge to your AI

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ServiceForge knowledge base record. Field-unverified unless technicians confirmed it. A teaching summary of the record, not a service manual. Export 2026-10-14.