Control of Air-Conditioning Compressor

Actuation of the air-conditioning compressor is dependent on the ambient temperature and the engine operation time. The compressor is switched off under + 3 °C, and switched on again at + 5 °C. The engine must have been running for at least 7 seconds.

The AC signal is output in the form of a PWM signal. The period is 280 ms, the pulse width in steps of 40 ms is dependent on the Energy Requirement Level (ERL) signal.

With maximum cooling ERL < 30, the signal is continuously high. With minimum cooling, Thigh is 40 ms. If the air-conditioning compressor is switched off (e.g. in economy mode), the signal is continually low.

As a result, the DME control module is able to estimate the working point of the compressor and to optimize idle speed regulation.