Valeooscope - Air Conditioning System Thermal comfort loop

F16 +ACC.

+CLIM

+BAT.

Coolant temperature sensor

A/C pressure sensing

Cooling fan

Fan low speed

Compressor cycling process When the air temperature is below or equal to the target value Tmin (about -1°C), the surface of the evaporator may freeze. The sensor detects this temperature and sends it to the control system, which switches off the compres- sor.

Compressor control

Fan high speed

11.9.2 The evaporator sensor The evaporator sensor is a temperature detector. Role: g Sensing the evaporator temperature g Preventing the freeze of the evaporator by stopping cold generation

Evaporator temperature

A/C start up and cool down

Evaporator freezing

ON OFF

Compressor cycling phase

Tmax

ON OFF

Tmin

OFF ON

Evaporator freezing

Time

ON

OFF

This causes a drop in the production of cold by the evaporator and a gradual rise in the temperature on its surface. The sensor then detects this increase in the tempe- rature and authorises the compressor to restart when the temperature reaches Tmax. A/C loops fitted with variable-cylinder and external control compressors do not need an evaporator sensor. The thermal power is adjusted in order to: g Avoid freezing on the evaporator g Provide greater comfort g Improve the efficiency of the system g Reduce the vehicle fuel consumption

Evaporator temperature

Tmin (°C)

Tmax (°C)

The compressor generally disengages when the detected temperature achieves -1°C, and re-enga- gement occurs at 4°C Location: Option1: The sensor is located in the air stream where the air leaves the evaporator Option2: The sensor is plugged on the evaporator’s fins and located in the coldest area

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