When switched on, the air-conditioning compressor on my Range Rover P38 4.6 pulls in for less than a second and drops out again. The electronic fault code is DTC3-32 ‘compressor clutch control circuit fault’.
If I connect the pin on the back of the HVAC (heating, ventilation and air-conditioning) unit to earth, the clutch pulls in and the aircon gives cold air. So, the circuit actually works and the gas circulation is good.
How does the system know that there’s a circuit fault? It can’t be the HVAC unit as that only ‘sees’ as far as the relay. Is there current sensing in the fusebox that tells the BCM (body control module)?
Nigel Elwell, Tamworth, Staffordshire
I don’t think these results are telling you that the circuit is broken in terms of an open circuit in a cable; rather that the compressor is switched off.
This happens if the refrigerant is low by about 20 per cent. The low pressure causes the BCM to signal to the HVAC to turn off the compressor. The fact that you can override the system and get cold air from the remaining 80 per cent charge doesn’t mean it doesn’t need a recharge.
Considering that even testing your BCM will cost you 50 quid and a repaired one £250-plus, I would say that a recharge is the first, and hopefully last, step.