The Rotax 965531 is a threaded engine temperature sensor probe used on Rotax 912 / 912S / 914 / 915 series engines to measure oil temperature, cylinder head temperature (CHT), or coolant temperature, depending on installation location and aircraft configuration.

It is a resistive thermistor-type sensor, meaning its electrical resistance changes with temperature and is interpreted by engine instruments or avionics systems.

Common applications include:

Oil temperature sensing (gearbox / oil system area)
Cylinder head temperature (CHT) monitoring
Coolant temperature (in liquid-cooled configurations or FADEC systems)
Key features include:

OEM Rotax temperature probe (P/N 965531)
Threaded installation (commonly M10 × 1.5) 
Thermistor-based resistance sensor (not thermocouple) 
Compatible with Rotax 912 / 914 / 915 engine families
Used for engine monitoring via Garmin, Dynon, UMA, etc. 
Direct engine installation into designated sensor port
Provides real-time temperature data to cockpit instruments
Aviation-certified for continuous engine monitoring use
Sensitive to wiring integrity (open circuit = false high readings)