Maquet Servo S: constant high internal temperature alarm
What happened
The ventilator kept raising a high internal temperature alert continuously during operation, with no related error code reported in the case.
What was checked
- Checked which software version was installed on the unit.
- Swapped the air gas module with a known-good one from another machine.
- Ran the ventilator on a test lung in volume mode and reviewed the waveforms and measured values.
- Located the temperature sensor, which sits in the O2 sensor connector, and inspected it.
- Leak-checked the gas path from the gas modules to the mixer module.
- Cleaned the sensor contact with alcohol.
Cause
In this case no single cause was confirmed. The engineers considered a dirty or poorly seated temperature sensor in the O2 sensor connector, together with a leaky gasket in the gas path from the gas modules to the mixer, the most likely reasons; if the unit was genuinely overheating, a failed cooling fan (commanded by the temperature sensor) was the probable culprit.
The cause is probable and was not fully confirmed.
What was done
In this case the fix was to clean the temperature sensor contact in the O2 sensor connector, check and reseat the gasket seal along the gas module path to the mixer, and replace the cooling fan if real overheating was confirmed as the likely source of the alert.
Safety
Isolate the ventilator from mains power before cleaning the sensor or opening the gas path, and complete the full pre-use check on a test lung before returning the unit to clinical use.
Lesson: A stubborn internal-temperature alarm can come from simple causes such as a dirty sensor contact, a tired gasket or a failing cooling fan, so check the sensor, seals and fan before swapping expensive modules.
Covered in the course: Ventilator Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.