Staying Cool With Electric A/C Compressor Service
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Staying Cool With Electric A/C Compressor Service

Electric air conditioning compressors have been around for quite some time now, so most of us have seen them or at least heard of their usage. While electric vehicles may have only accounted for just under 3% of vehicle sales in 2020, that number is projected to be 20% by 2030. That means more of these electrically cooled vehicles will be rolling into your shop. The basic operation of the air conditioning remains the same. We still need a refrigerant to absorb heat from the cabin via the evaporator and return it back into a useable liquid with the help of the condenser. What has changed is how we service them. 

First and foremost, let’s talk about safety. Safety is extremely important when working with high voltage. These compressors can have as much as 400 volts to operate, such is the case with Tesla. That’s a lot of voltage and nothing you want to mess around with! These high-voltage (HV) circuits can be identified by the orange wiring that is routed to them. If replacement of a compressor is required, always follow the manufacturers’ procedures to shut down the HV source.

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These procedures will always require the usage of HV Class 0/1,000-volt gloves, along with a leather glove on top, to protect the gloves from damage. A category III-rated multi-meter is also required to safely verify the high-voltage components being serviced are no longer live circuits with high voltage. Finally, it is always a recommended practice to have a second technician nearby with a high-voltage insulated emergency hook in the event of accidental high-voltage exposure. This hook will allow a technician to be safely pulled away from the vehicle as the high voltage will tend to grab the affected person, not allowing them to be released from it on their own. 

It is important to pay attention to the type of oil used in an eCompressor, as it usually differs from the oil used in mechanical-driven compressors. There are countless manufacturer TSB’s regarding this topic. HV compressors require special Polyol Ester (POE) A/C refrigerant oil that is non-conductive. The specific type of oil is identified by the vehicle manufacturer. All non-conductive POE oils are not the same! It is extremely important to not use any compressor oil other than what is recommended by the manufacturer.  This oil provides high dielectric properties, which helps to maintain the integrity of the compressor’s electrical windings and prevent high voltage from bleeding through the compressor itself, and possibly electrocuting the technician.

It is also important to never mix PAG oil with these systems. Just 1% of PAG oil in the system can lower the insulation resistance of a compressor from over 10 mega-ohms to under 1 mega- ohm. This can cause a DTC to set and even shut down the compressor itself. Many vehicle manufactures will require replacement of the entire A/C system if PAG oil has cross-contaminated the system. 

And, finally, pay close attention to the dye you are adding to these systems. Just as the wrong oil can contaminate a system, the same thing can happen if the wrong dye is used. There is a specific dye for electric compressors. Hybrid electric vehicle leak detection dye is Polyol Ester-based and is specific to the vehicle.

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The dye used for non-hybrid electric vehicles is PAG oil, which is hygroscopic. Using it in a hybrid vehicle, even in the smallest amount, can create an air conditioning compressor failure. The oil in the dye breaks down the insulating properties of the windings on the electric motor portion of the compressor. These windings are immersed in compressor oil, and ester oil is used to protect the insulation on the windings to prevent electrical leakage. The addition of PAG oil into a hybrid air conditioning system designed for ester oil may result in an air conditioning system malfunction.

A straight-forward approach to avoid cross-contamination is to use dedicated hoses and injectors for each type of refrigerant oil. A/C equipment that has been used for conventional A/C systems can contaminate the HV-powered system.

Servicing electric A/C compressors will require a different approach and some special precautions that are different than the belt-driven compressors, but if you follow the recommended service procedures, your repair will go as “cool” as the air coming out of those A/C vents.

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