Patient warming systems

Stryker Mistral-Air Plus: troubleshooting and error codes

The ServiceForge knowledge base holds 18 documented symptoms for the Stryker Mistral-Air Plus, with 33 ranked causes, 35 diagnostic checks with test points and expected values, and 2 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

Over temp alarm and warming unit stopped

Unit triggers over-temperature alarm and ceases heating operation.

Ranked causes

1. Faulty inductor (rare)
2. Temperature (heater/blower housing) maybe out of calibration (occasional)
3. Faulty PCB (rare)
4. Faulty temperature sensors (occasional)

First check

Allow unit to cool and monitor for condition persistence

Test point: Unit temperature
Expected: Unit cools without repeating alarm

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

Unit does not turn on caution

Device fails to power up when plugged in and switched on.

Ranked causes

1. Unplugged or damaged power cord (common)
2. No power to outlet (common)
3. Poor or loose wire connections (occasional)
4. Blown fuses at PCB (occasional)

First check

Inspect power cord for damage and proper connection

Test point: Power cord connector
Expected: Cord plugged in, no visible damage

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

Unit heats but turns off before reaching set temperature

Heater operates initially but shuts off before target temperature is achieved.

Ranked causes

1. Poor or loose wire connections (occasional)
2. Faulty heater (occasional)
3. Faulty temperature sensors (occasional)
4. Obstructed Filter or Blower wheel (occasional)

First check

Verify heater, sensor, and inductor connections to PCB

Test point: PCB connectors for heater and temperature sensors
Expected: All connections secure

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

Unit turns on but does not blow air

Unit powers up but no air flow is produced; blower is not operating.

Ranked causes

1. Air inlet obstructed (common)
2. Blower wheel is obstructed (common)
3. Poor or loose wire connections (occasional)
4. Faulty PCB (rare)

First check

Inspect air inlet and filter for obstruction

Test point: Air inlet and filter
Expected: No obstructions, clean filter

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

Unit alarms at too low or too high temperature

Unit triggers temperature alarms at incorrect threshold levels.

Ranked causes

1. Temperature (heater/blower housing) maybe out of calibration (common)
2. Faulty temperature sensors (occasional)
3. Faulty PCB (rare)

First check

Calibrate temperature sensor circuit

Test point: Temperature sensor at PCB
Expected: Calibration completed

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

Unit turns on but temperature settings cannot be selected

Unit powers up but control panel does not respond to temperature adjustment commands.

Ranked causes

1. Faulty or loose membrane switch (switch contacts or header) (common)
2. Faulty control board (occasional)

First check

Inspect membrane switch connection to control board

Test point: Membrane switch connector
Expected: Red/white wire at top, connection secure

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

Calibration: Temperature accuracy at multiple setpoints

Verify temperature measurement accuracy at 43°C, 38°C and 32°C setpoints

Ranked causes

1. Temperature sensor drift or calibration offset (unknown)

First check

Measure tube temperature at 43°C setpoint

Test point: Test tube with thermometer
Expected: Between 41.5 and 44.5°C, +/- 1.5°C

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

Low temperature alarm not triggering patient safety

Alarm LED and buzzer should activate when tube temperature drops below 37°C during test

Ranked causes

1. Temperature control or alarm detection malfunction (unknown)

First check

Set temperature setpoint to 32°C

Test point: Control panel display
Expected: 32°C selected

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

No low temperature alarm due to temperature overshoot patient safety

Low temperature alarm or primary over temperature alarm fails to enable, possibly due to temperature overshoots during control

Ranked causes

1. Temperature control instability causing overshoot (occasional)

First check

Monitor for temperature overshoot during heating cycles

Test point: Temperature sensor reading during control
Expected: Temperature within expected range boundaries without overshooting

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

Over temperature alarm patient safety

Audible alarm activated; LED flashes red (primary alarm) or glows solid red (secondary alarm)

Ranked causes

1. Over temperature condition (unknown)

Primary over temperature alarm patient safety

Flashing red LED on control panel with triple beep alarm every 25 seconds when unit temperature reaches or exceeds 46.5°C

Ranked causes

1. Unit temperature at or above 46.5°C (common)

First check

Verify unit temperature reading

Test point: Control panel display
Expected: ≥ 46.5°C

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

Primary over temperature alarm not triggering patient safety

Alarm LED should blink and buzzer activate when temperature reaches primary overheat threshold (46.5°C to Tsecondary - 2.0°C)

Ranked causes

1. Temperature sensor or alarm detection circuit malfunction (unknown)

First check

Set temperature setpoint to 38°C

Test point: Control panel display
Expected: 38°C selected

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

Replace air filter

Remove dust-accumulated filter and install new filter to restore warming unit efficiency

Ranked causes

1. Dust accumulation in air filter (common)

First check

Visual inspection of filter condition

Test point: Air filter
Expected: Excessive dust accumulation or Service Indicator alert

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

Routine maintenance required

Unit requires periodic service including filter replacement and hour meter reset after scheduled intervals

Ranked causes

1. Annual service interval or 500-hour threshold reached (common)

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

Secondary over temperature alarm patient safety

Solid red LED flashing with short audible alarm when temperature exceeds (T primary + 2) to 56.4°C; heater and blower shut down

Ranked causes

1. Unit temperature exceeds (T primary + 2) to 56.4°C threshold (rare)

First check

Verify unit temperature is in critical range

Test point: Control panel display
Expected: (T primary + 2) to 56.4°C

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

Service indicator activated at ≥500 hours use

Service indicator light displays; indicates routine maintenance and filter replacement required; hour meter needs reset

Ranked causes

1. Scheduled 500-hour maintenance interval reached (common)

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

Under temperature alarm patient safety

Red LED indicates temperature has fallen 6°C below the set temperature

Ranked causes

1. Unit temperature 6°C below set point (occasional)

First check

Verify temperature deficit

Test point: Control panel display
Expected: 6°C below set temperature

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

Verify filter presence before service caution

Ensure filter is installed before operating unit to prevent damage and maintain effectiveness

Ranked causes

1. Missing air filter (rare)

First check

Verify filter installed

Test point: Filter housing
Expected: Filter present with black seal facing fan

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

Error codes

Code	Meaning	Trigger	Severity
`Audible Alarm Suppression (solid orange LED)`	Audible alarm temporarily suppressed for 3 minutes	Audible Alarm Suppression button pressed	info
`Service Alarm (red LED at wrench)`	Routine maintenance required; unit has been used for ≥500 hours	Operating hours reach 500 or greater	warning

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.