Readying your shop for hybrid A/C service

July 21, 2014
Hybrid air conditioning systems present some unique challenges. Is your shop equipped to handle them?

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.

Bosch RRR machine. Photo Courtesy of Bosch

Lets talk more about the actual RRR machines. There are several options available and they all have some means to help the technician to properly service a high voltage hybrid system. The Bosch and RTI hybrid RRR machine has a sub-menu that allows you to tell the machine you are servicing a hybrid so that you can run a purge of the lines prior to service. Robinair takes it one step further and asks the technician if a hybrid is being serviced. If the answer is yes the machine runs an internal purge with refrigerant to remove any PAG oil from the lines. Robinair’s Wagaman says, “The potential for cross contamination is during recharge if there is PAG in the lines. If you have a machine you use in normal R134A/PAG services you can still recover and evacuate a hybrid system with it.”

These machines can cost upwards of $4,000 but most of them are not single purpose machines. You can use these machines for all of your regular A/C service too. Most area fully automatic so you can setup all your specs and walk away while it does the job. If a machine like that is not in your current tool budget there is another way to still perform A/C work on high voltage hybrid systems. According to AirSept, “To allow the use of non-J2788H RRR machines on certain hybrids (and conventional systems as well), an add-on filter known as the “A/C charge Guard” is available. It is designed to remove oil, dye, and other liquid or particulate contaminants from refrigerant during recharge. This special filter is placed in series between the RRR machine and the vehicle. It vaporizes the refrigerant, and traps and holds the vast majority of non-vaporous materials (including oil), so they cannot enter the vehicle’s A/C system. The filter eliminates the need to purchase separate equipment to recharge hybrid vehicles High voltage A/C compressors.”

A final suggestion is if you are replacing a component of the high voltage A/C system the service precautions are no different than any other hybrid vehicle repairs. Prior to work you must disable the high voltage system and make sure it is all powered down. These components are very deadly and very expensive so it is mission critical to read all of the procedure before starting and make sure you have the proper tools to complete the operation safely.

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