E 320 4MATIC Sedan (210.082) V6-3.2L (112.941) (1999)
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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
push-button 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.
Stage 2
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).
