S 600 (140.057) V12-6.0L (120.982) (1998)
Coolant Temperature Sensor / Switch HVAC: Description and Operation
Air Conditioning Coolant Temperature Sensor
The air conditioning coolant temperature sensor serves for measuring the coolant temperature.
The ECT sensor sends a resistance value corresponding to the coolant temperature via the instrument cluster and the serial interference (K1) to the
pushbutton control module.
Here the value is processed and the A/C compressor is switched off in two stages as follows:
Stage 1
At a coolant temperature >123 °C the duty factor is reduced by 50 %. In this case the A/C compressor is switched on in cycles, i.e. off approx. 20 sec
and on approx. 20 sec.
If the coolant temperature drops to below 123 °C the A/C compressor is switched on again permanently.
Stage2
At a coolant temperature >127 °C the A/C compressor is switched off completely.
When the coolant temperature drops to below 127 °C the A/C compressor is switched back on in the cycled mode (stage 1).