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Readying your shop for hybrid A/C service

Monday, July 21, 2014 - 07:00
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Donny Seyfer, ABRN Contributing Editor, contributed to this article.

Servicing hybrid air conditioning systems is either business as usual or new machines, new oils and different procedures. The trick is identifying which. Let’s get the business as usual hybrids out of the way first. If you are working on a Ford Escape, Mercury Mariner or Mazda Tribute hybrid, they have a belt and are traditional A/C systems. The Saturn Vue is also belt driven. They use conventional R134A, along with PAG oil. There are not many, but if the compressor is driven by a belt, it is most likely using PAG oil and conventional service techniques.

A high-voltage A/C compressor is identifiable by the orange wire loom. Photo Courtesy of Denso

Nearly every other hybrid vehicle I looked up has a high voltage A/C compressor (HVACC for our purposes). That includes the big Escalade and Suburban all the way down to the Toyota Yaris hybrid. Here again, if you do not see a belt driving the compressor it is an HVACC. Another tip off is that large orange cable entering the compressor indicating a high voltage line.

The secret is in the oil when it comes to hybrid vehicles with High Voltage A/C compressors. According to Denso, who manufacturers many of these HVACC, only 1% PAG oil can cause failure. Everything you do to service these A/C systems revolves around an absolute requirement to have pure POE oil in their systems.

Why is it so critical to have pure POE oil in the hybrid A/C systems? The answer is that the compressor houses an electric motor swimming in POE oil that is powered by the high voltage traction battery that also runs the motor/generator that is part of the hybrid propulsion system. POE and its counterpart PVE oil are specially designed to provide very high dielectric properties – they insulate electrical components. PAG oil on the other hand is conductive. A simple illustration would be one of those movies where a guy gets killed in the bath tub by a blow drier falling in with him. Fill a hybrid HVACC up with PAG oil and you will get the same effect. Fortunately these hybrid high voltage A/C systems have voltage leakage sensors and will shut down the system if a leak is detected.

PVE oil has been replaced in Kia and Hyundai vehicles by POE oil (see TSB). Kia says that the two oils are compatible so a full flush is not necessary but they point out that the POE oil is better.

The equipment involved in servicing hybrid A/C systems is different. There is an SAE (Society of Automotive Engineers) standard that dictates equipment requirements.  According to the Mobile Air Conditioning Society (MACS) and A/C specialty tool maker AirSept the key component of  the SAE J2788 standard is the isolation of refrigerant oil. If the machine is a hybrid spec J2788 machine it does not have an oil injector as do many non-hybrid A/C Recover, Recycle, Recharge (RRR) machines. “To maintain the >.1% PAG oil required by the SAE spec hybrid RRR machines cannot include an oil injection system,” say Tim Wagaman – Senior Product Manager for A/C and Fluid Products at Robinair. Oil must be injected into the system through a separate injector. Wagaman recommends have a specific injector tool designated for PAG and POE that are only used for that oil and carefully labeled to avoid confusion.  A wise practice might be to label the POE – Hybrids with electric compressors and the PAG oil – Never use in Hybrids. The main reason for the concern is cost. The list price of a 2010 Escalade HVACC for example is $3004 and you can bet they are not sitting on the shelf at the dealer. That will have you in negative profit margins really quick on a front-end collision repair and it won’t stop there because you will have to flush the entire system and replace the receiver drier to boot.

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