Hyperthermia machines

Gaymar Medi-Therm II: troubleshooting and error codes

The ServiceForge knowledge base holds 37 documented symptoms for the Gaymar Medi-Therm II, with 113 ranked causes, 138 diagnostic checks with test points and expected values, and 13 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

Blanket won't heat in AUTO or MANUAL mode

Blanket temperature does not reach setpoint when heating is activated; temperature remains below target

Ranked causes

1. Pump not running (common)
2. Inadequate water flow (common)
3. Cold solenoid SV1 stuck open or hot solenoid SV2 stuck closed (occasional)
4. Hot solenoid SV2 not energized (occasional)
5. Hot solenoid SV2 coil shorted (occasional)
6. Heater element open or shorted (occasional)
7. Heater not energized (occasional)
8. Pin 7 of U51 not at 0 VDC relative to pin 10 (rare)
9. Pin 11 of U51 not at 0 VDC relative to pin 10 (rare)
10. Optocoupler U1 input not pulled low (rare)
11. Optocoupler U7 input not pulled low (rare)
12. Optocoupler U8 input not pulled low (rare)
13. No line voltage at Q3 output (rare)
14. No line voltage at Q8 output (rare)
15. No line voltage at Q9 output (rare)
16. No line voltage at TB1 terminals 1 and 3 (rare)
17. No line voltage at TB1 terminals 2 and 3 (rare)
18. No line voltage at TB1 terminals 11 and 8 (rare)
19. Temperature sensor RT2 inaccurate (rare)

First check

Verify pump is running

Test point: Pump motor
Expected: Pump running

11 more checks with pass and fail actions, 21 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Check Water Flow alert is on

Water flow alarm activated; blanket temperature does not reach setpoint

Ranked causes

1. Hoses not connected properly (common)
2. Blankets, hoses or connectors pinched or occluded (common)
3. Blankets or hoses excessively dirty (occasional)
4. Pump motor not running (common)
5. Flow switch S5 failure (occasional)
6. Cold solenoid SV1 shorted (occasional)
7. Hot solenoid SV2 shorted (occasional)
8. Impeller broken or cracked (occasional)
9. Control/display board failure (rare)
10. Board-to-board connection failure (rare)
11. Base-to-power supply board connection failure (rare)
12. Q8 or Q9 triac failure (rare)
13. Solenoid coil not energized (rare)

First check

Verify hose connections

Test point: SUPPLY and RETURN ports
Expected: One hose connected to SUPPLY, one to RETURN

11 more checks with pass and fail actions, 16 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Blanket will not cool high voltage

Refrigeration system faulty; blanket display temperature not within 1.8°F (1°C) of setpoint or reservoir cannot reach 42.8°F (6°C)

Ranked causes

1. Cold solenoid SV1 not energized or stuck closed (common)
2. Dirty or restricted refrigeration condenser (common)
3. Refrigeration unit may have lost its charge (occasional)
4. Hot solenoid SV2 stuck open or control/display board failure (occasional)
5. Pump not running or inadequate flow (common)
6. Compressor not running or thermal overload tripped (occasional)
7. Power supply board or relay failure (occasional)
8. Reservoir temperature probe RT1 failure or control/display board failure (occasional)

First check

Check if steel object is attracted to center top of valve (magnetic test)

Test point: Valve center top
Expected: Yes = solenoid working; No = solenoid may be faulty

26 more checks with pass and fail actions, 9 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Pump motor not running

Pump does not start or run; no fluid circulation detected

Ranked causes

1. Unit not in AUTO or MANUAL mode (common)
2. Pump winding shorted (occasional)
3. Optocoupler U2 input not pulled low (occasional)
4. No line voltage at Q4 output (occasional)
5. Pin 8 of U51 not at 0 VDC relative to pin 10 (rare)
6. Board-to-board connection failure (rare)
7. Base-to-power supply board connection failure (rare)
8. No line voltage at TB1 terminals 6 and 8 (rare)

First check

Verify operating mode setting

Test point: Unit mode selector
Expected: Unit in AUTO or MANUAL mode

5 more checks with pass and fail actions, 9 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

RFU Code 1: Temperature sensor reading out of range

Machine displays RFU Code 1 in Service Mode 1, indicating measured values from RT1 or RT2 are not within 32°F to 122°F (0°C to 50°C) range.

Ranked causes

1. RT1 sensor faulty (common)
2. RT2 sensor faulty (common)
3. Faulty signal lines between control/display board and RT1 (occasional)
4. Faulty signal lines between control/display board and RT2 (occasional)
5. Control/display board temperature measurement circuitry failure (occasional)
6. Controller failure (rare)

First check

Measure RT1 actual temperature

Test point: RT1 sensor
Expected: Between 32°F and 122°F (0°C and 50°C)

4 more checks with pass and fail actions, 6 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

RFU Code 8: Blanket probe reading faulty

Machine displays RFU Code 8 in Service Mode 1, indicating the blanket probe (RT2) reading is faulty.

Ranked causes

1. RT2 sensor faulty (common)
2. Faulty signal lines between control/display board and RT2 (occasional)
3. Control/display board temperature measurement circuitry failure (occasional)
4. Controller failure caused RT2 reading outside acceptable range (rare)

First check

Disconnect RT2 connector and measure signal line resistance

Test point: Pins 3 and 5 of connector P6
Expected: Between 811 and 7355 ohms

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

RFU Code 9: Reservoir probe reading faulty

Machine displays RFU Code 9 in Service Mode 1, indicating the reservoir probe (RT1) reading is faulty.

Ranked causes

1. RT1 sensor faulty (common)
2. Faulty signal lines between control/display board and RT1 (occasional)
3. Control/display board temperature measurement circuitry failure (occasional)
4. Controller failure caused RT1 reading outside acceptable range (rare)

First check

Disconnect RT1 connector and measure signal line resistance

Test point: Pins 2 and 9 of connector P6
Expected: Between 811 and 7355 ohms

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

Algae growth in fluid system caution

Cloudiness, discoloration, or biological growth visible in water circulation system or blankets; reduced flow rate or foul odor from system.

Ranked causes

1. Tap water use or infrequent water changes (common)
2. Excessive algaecide concentration (occasional)
3. Use of bleach in cleaning (rare)

First check

Inspect water clarity and system appearance

Test point: Fluid reservoir and blanket tubes
Expected: Clear distilled water, no visible growth or discoloration

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

Chassis condition degraded or corroded caution

Rust, corrosion, or discoloration visible on chassis exterior; exterior screws loose or corroded; casters not functioning smoothly; visible dirt or debris in ventilation areas.

Ranked causes

1. Moisture exposure or environmental corrosion over time (occasional)
2. Caster wheels damaged or locked (occasional)
3. Accumulated dirt in ventilation vents and cooling fins (common)

First check

Visually inspect chassis for corrosion and discoloration

Test point: External chassis surfaces and frame
Expected: Clean, minimal rust or corrosion; no paint peeling or heavy discoloration

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

Flow rate below minimum specification patient safety

Flowmeter reading lower than specified minimum; machine unable to deliver adequate circulating flow during heating or cooling mode; slow temperature response.

Ranked causes

1. Air trapped in pump system after complete drain (occasional)
2. Blocked or restricted flow path in blanket connector hose (occasional)
3. Pump cavitation or bearing wear (rare)

First check

Fill machine water reservoir to proper level

Test point: Reservoir and float stem green band indicator
Expected: Green band on float stem fully visible; machine filled to operating level

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

RFU Code H: Microprocessor received shutdown signal from base

Machine displays RFU Code H, indicating a shutdown signal was received from the base thermostats (S1, S2, S3).

Ranked causes

1. S1 (low temperature thermostat) open or faulty (common)
2. S2 or S3 (high temperature thermostat) open or faulty (common)
3. Power supply board REMOVE FROM USE NOW/MACHINE SHUTDOWN circuitry failure (occasional)

First check

Check thermostat continuity

Test point: TB1 terminals 10 and 8
Expected: 0 ohms (closed)

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

Attachment plug damaged or deteriorated high voltage

Power plug shows visible wear, cracks, or discoloration; pins corroded or pitted; difficult to insert into outlet; loose connection with cord.

Ranked causes

1. Age-related deterioration or prior damage to plug (occasional)
2. Corrosion on plug pins or contacts (occasional)

First check

Inspect attachment plug for physical damage and corrosion

Test point: Power cord plug and pins
Expected: No cracks, discoloration, or corrosion; pins intact and shiny; plug seats firmly in outlet without force

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

AUTO mode blanket water exceeds 42°C limit with simulated patient temperature patient safety

During AUTO mode testing with simulated 37°C patient probe resistance, machine allows blanket water to exceed 42°C setpoint limit; machine does not properly limit blanket water temperature in AUTO mode.

Ranked causes

1. Blanket water limit controller malfunction in AUTO mode (occasional)
2. Patient probe simulator resistance incorrect or connection unstable (occasional)

First check

Prepare machine for AUTO mode test

Test point: Machine water fill level and mode selector
Expected: Machine filled to green band level; ready to enter AUTO mode

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

Blanket water temperature not matching display or out of tolerance patient safety

Display shows incorrect temperature reading compared to actual water temperature measured with external thermometer; temperature reading on display is unstable or fluctuates excessively.

Ranked causes

1. Temperature sensor out of calibration or malfunction (occasional)
2. Loose or corroded sensor wiring connection (occasional)

First check

Connect test equipment and set initial temperature setpoint

Test point: Test setup per figure 13 with TPT9 tester and mercury thermometer
Expected: Setup completed; machine in MANUAL mode; setpoint set per INSPECTION FORM item i

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

Calibration: High temperature backup thermostat trip points patient safety

Measure the actuation temperatures at which the machine's redundant safety thermostats S2 and S3 shut down the system to verify they operate within specification for the model.

Ranked causes

1. Thermostat trip point verification required (common)
2. Thermostat malfunction or independent shutdown failure (rare)

First check

Fill machine with distilled water

Test point: float stem green band
Expected: green band fully visible

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

Circuit breaker worn or intermittent caution

Machine shuts off unexpectedly or repeatedly during operation; no error code displayed; cycling circuit breaker on and off does not restore operation reliably; no other apparent failure symptoms.

Ranked causes

1. Worn circuit breaker contacts or loose terminals (common)
2. Loose circuit breaker terminals (occasional)

First check

Inspect circuit breaker physical condition and terminals

Test point: Circuit breaker and push-on terminals at rear
Expected: No discoloration, no heating marks, terminals fully seated and snug

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

Cold water reservoir controller not maintaining setpoint temperature patient safety

Machine unable to cool water to setpoint temperature; compressor does not cycle off as expected; water temperature drifts during COOL mode operation.

Ranked causes

1. Compressor not cycling off at target setpoint (occasional)
2. Thermostat sensor malfunction or loose connection (rare)

First check

Fill machine to operating level and connect test equipment

Test point: Water reservoir and TPT9 test equipment connections
Expected: Green band on float stem fully visible; test setup per figure 13 with return line connected to TPT9 tester (blanket optional for speed)

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

Level switch not actuating at proper water level patient safety

ADD WATER indicator remains off when fluid level is low; indicator does not turn off when water is refilled; bobber float mechanism appears stuck or unresponsive.

Ranked causes

1. Bobber float stuck or not seating properly on drain screen (occasional)
2. ADD WATER switch contact corrosion or loose wiring (occasional)

First check

Fill machine to proper operating level

Test point: Water reservoir and float stem green band
Expected: Green band on float stem fully visible; ADD WATER indicator off

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

Line cord or strain relief damaged high voltage

Visible cuts, cracks, or insulation damage on power cord; burn marks or melting at strain relief ends; intermittent power loss or arcing sounds.

Ranked causes

1. Physical damage to line cord or strain relief during use or storage (occasional)
2. Poor strain relief condition or improper seating (occasional)

First check

Visually inspect entire line cord for damage

Test point: Line cord from plug to machine connector
Expected: No cuts, cracks, or discoloration; insulation intact; no exposed wires

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

RFU Code 4: Compensation resistor 1 reading too high

Machine displays RFU Code 4, indicating compensation resistor R12 on control/display board reading is above specification.

Ranked causes

1. R12 compensation resistor out of specification (common)
2. Control/display board temperature measurement circuitry failure (occasional)

First check

Measure R12 resistance

Test point: R12 on control/display board
Expected: 816 ohms ±0.1%, ±0.1%

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

RFU Code 5: Compensation resistor 1 reading too low

Machine displays RFU Code 5, indicating compensation resistor R12 on control/display board reading is below specification.

Ranked causes

1. R12 compensation resistor out of specification (common)
2. Control/display board temperature measurement circuitry failure (occasional)

First check

Measure R12 resistance

Test point: R12 on control/display board
Expected: 816 ohms ±0.1%, ±0.1%

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

RFU Code 6: Compensation resistor 2 reading too high

Machine displays RFU Code 6, indicating compensation resistor R13 on control/display board reading is above specification.

Ranked causes

1. R13 compensation resistor out of specification (common)
2. Control/display board temperature measurement circuitry failure (occasional)

First check

Measure R13 resistance

Test point: R13 on control/display board
Expected: 7320 ohms ±0.1%, ±0.1%

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

RFU Code 7: Compensation resistor 2 reading too low

Machine displays RFU Code 7, indicating compensation resistor R13 on control/display board reading is below specification.

Ranked causes

1. R13 compensation resistor out of specification (common)
2. Control/display board temperature measurement circuitry failure (occasional)

First check

Measure R13 resistance

Test point: R13 on control/display board
Expected: 7320 ohms ±0.1%, ±0.1%

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

Test lights or alarm indicators not functioning patient safety

LEDs on display panel do not illuminate; audible alarm does not sound during test; status legends or temperature displays remain dark when TEST LIGHTS button pressed.

Ranked causes

1. Burned-out LED or defective lamp (common)
2. Loose or corroded wiring connection to indicator lamps or speaker (occasional)

First check

Perform TEST LIGHTS button function test

Test point: Display panel LEDs and audible alarm
Expected: Right and left halves light and blank alternately; FLOW OK, HEAT, IN-TEMP, COOL, ALERT with four triangular indicators, three mode legends and SELECT all lit; displays show '888', '888.8', '888.8'; temperature scale and setpoint lines lit; audible alarm sounds

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

Calibration: Current leakage chassis high voltage

Verify chassis current leakage does not exceed safety limits in all operating modes

Ranked causes

1. Current leakage exceeds limit (rare)

First check

Measure leakage with machine grounded

Test point: Chassis to ground
Expected: Not to exceed 10 microamps, ≤ 10 microamps
Tools: Leakage current meter

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

Calibration: Current leakage patient probe patient safety

Verify patient probe current leakage does not exceed safety limits with foil wrapping simulation

Ranked causes

1. Patient probe current leakage exceeds limit (rare)

First check

Wrap patient probe with metal foil

Test point: Patient probe entire length
Expected: Fully wrapped

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

Calibration: Grounding resistance high voltage

Verify chassis grounding resistance is within safety specification

Ranked causes

1. Grounding resistance exceeds specification (rare)

First check

Measure grounding resistance with ohmmeter

Test point: Grounding pin on line cord attachment plug to exposed chassis metal
Expected: Less than 0.5 ohms, < 0.5 ohms
Tools: Ohmmeter

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

Calibration: Low temperature backup thermostat (S1) caution

Verify trip point of low temperature backup thermostat to protect against freezing

Ranked causes

1. Thermostat trip point out of specification (unknown)

First check

Drain machine completely

Test point: Reservoir and circuit
Expected: Empty

3 more checks with pass and fail actions, 5 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Patient temperature display

Verify patient temperature display accuracy using resistive simulation of probe values

Ranked causes

1. Display not within tolerance (unknown)

First check

Fill reservoir with distilled water

Test point: Float stem green band
Expected: Fully visible

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

Calibration: Reset RFU code

Reset stored REMOVE FROM USE code to zero before returning machine to service

Ranked causes

1. Previous RFU code retained in memory (occasional)

First check

Enter service mode 1

Test point: Control panel service button
Expected: Service mode 1 active; displays RFU code and software version

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

Calibration: Thermostat verification patient safety

Verify that each backup thermostat (S2 and S3) independently causes machine shutdown to confirm redundant safety circuit operation.

Ranked causes

1. Safety thermostat functional verification required (common)

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

Compressor shipping brace not removed before operation patient safety

Machine has not been placed into service after delivery; compressor contains restraint brace to prevent damage during shipping.

Ranked causes

1. Lack of awareness of shipping brace requirement or procedure (common)

First check

Verify compressor shipping brace has been removed

Test point: Compressor area per figure B on page 86
Expected: No shipping brace present; compressor mounting secure and in normal operating position

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

Compressor unit may have lost refrigerant charge high voltage

Low pressure on refrigeration circuit; compressor cannot cool adequately.

Ranked causes

1. Refrigerant leak in system (common)

First check

Visually inspect all refrigeration lines, fittings, service valves, compressor, and condenser for oil residue, corrosion, or damage

Test point: Entire refrigerant circuit
Expected: No visible signs of leakage or damage

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

Concealed damage upon receipt caution

Physical damage to machine visible after unpacking; cracks, dents, or broken components observable during initial inspection.

Ranked causes

1. Shipping damage during transport (occasional)

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

Pump motor bearing wear or noise caution

Squealing, grinding, or rattling sounds from pump; motor does not rotate smoothly or pump fails to circulate water.

Ranked causes

1. Dry pump motor bearings due to insufficient lubrication (common)

First check

Inspect pump motor for oil ports and lubrication level

Test point: Pump motor label locations
Expected: Visible oil ports per label; no signs of drying or rust

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

Quick-disconnect fittings stiff or difficult to engage caution

Connector hose will not attach smoothly to machine fittings; excessive force required to engage quick-disconnects; potential leak risk at connection points.

Ranked causes

1. Lack of lubrication on quick-disconnect fittings (occasional)

First check

Test quick-disconnect engagement resistance

Test point: Machine supply and return fittings and blanket connectors
Expected: Smooth engagement with moderate hand pressure, no grinding or resistance

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

Reduced compressor efficiency caution

Compressor runs longer than normal, machine takes extended time to reach setpoint temperature, or insufficient cooling/heating capability.

Ranked causes

1. Dirt accumulation on condenser coils and cooling fins (common)

First check

Inspect condenser coils and cooling fins for dirt accumulation

Test point: Rear interior of machine near compressor
Expected: Clean coils and fins free of visible dirt and debris

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

Error codes

Code	Meaning	Trigger	Severity
`RFU [–]`	CHECKSUM failure	Software checksum validation failure	error
`RFU 1`	Temperature sensor reading out of range	RT1 or RT2 measured values outside 32°F to 122°F (0°C to 50°C) range	error
`RFU 2`	Conversion failure	A/D converter or temperature conversion circuit malfunction	error
`RFU 3`	Conversion failure	Temperature conversion circuit malfunction	error
`RFU 4`	Compensation resistor 1 reading too high	R12 on control/display board resistance above specification	error
`RFU 5`	Compensation resistor 1 reading too low	R12 on control/display board resistance below specification	error
`RFU 6`	Compensation resistor 2 reading too high	R13 on control/display board resistance above specification	error
`RFU 7`	Compensation resistor 2 reading too low	R13 on control/display board resistance below specification	error
`RFU 8`	Blanket probe reading faulty	RT2 sensor or signal integrity failure	error
`RFU 9`	Reservoir probe reading faulty	RT1 sensor or signal integrity failure	error
`RFU E`	RAMTEST failure	Random access memory self-test failure	error
`RFU H`	Microprocessor received shutdown signal from base	S1, S2, or S3 thermostat opened or power supply board shutdown circuit activated	error
`RFU L`	RAMTEST failure	Random access memory self-test failure	error

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

Community

0 fixes logged by technicians through their AI, with outcomes, for this model.

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