Alan Povey, quality, warranty & technical representative at Mahle Aftermarket, said air conditioning compressors for electric and hybrid vehicles differ from belt-driven models in many ways and it’s therefore important to follow best-practice tips to ensure maintenance is carried out efficiently.
As electrically driven compressors are hermetically sealed, the absence of a drive shaft for the belt drive means that refrigerant cannot escape via the shaft seals.
The electric motor for the drive is located within the compressor housing. Since the motor encounters refrigerant and refrigerant oil, only oil with insulating properties may be used. There is a risk of a short circuit if moisture enters the refrigerant circuit. Polyalphaolefin multigrade oils are therefore preferred due to their non-hygroscopic properties.
However, technicians should always follow the vehicle manufacturer’s specifications when selecting the refrigerant and compressor oil. Choosing the correct refrigerant oil, as well as regular air conditioning services, are crucial to the safe operation of electric air conditioning compressors.
Electric compressors generally do not have an oil drain plug, so it is not possible to adjust the system oil quantity via the compressor. The air conditioning system must therefore be flushed before installing a new compressor. This is the only way to ensure that the system is free of oil residues and to avoid overfilling.
All non-flushable components must be replaced, as must the drier.
Many vehicle manufacturers use special programmes when commissioning a new air conditioning compressor. By means of a diagnostic tester, these programmes ensure a slow start-up and therefore prevent a sudden intake of compressor oil from causing consequential damage such as a hydraulic shock.