Use caution when recharging A/C systems on hybrid vehicles

This post comes to us from MACS member Airsept. (

Some hybrid vehicles use air conditioning compressors that are operated by an electric motor instead of a drive belt. The motor’s insulated windings are immersed in the compressor’s lubricating oil. The oils used in these compressors have high dielectric (non-conductive) properties. DENSO has produced a chart showing that as little as 1% contamination by an improper oil can affect the dielectric properties. If a different type of oil somehow makes its way into one of these compressors, and if the insulation on the windings has become damaged or compromised, a variety of problems may occur.

● The greatest risk is that the oil may conduct high voltage to the compressor case or connected components. A person may receive an electric shock if they touch the compressor, engine, etc. and an appropriate ground.

● Sensors in the compressor case can detect very small voltage leaks. Once a leak is detected, the control system will shut down the compressor.

As drastic as it may seem, in service bulletins, some hybrid vehicle manufacturers state that all of the refrigeration system components must be replaced if oil cross contamination has occurred.

Some shop equipment may introduce an unacceptable level of oil contamination if used to charge refrigerant into a hybrid vehicle with an electric motor driven compressor. Residual incorrect oil may remain in the equipment’s hoses and internal plumbing, and be delivered into the system during the charge process.

Recovery/ recycling/ recharge (RRR) machines that meet SAE specification J2788H are acceptable for use on hybrid vehicles with electrically driven compressors, and they may also be used for conventional A/C systems. These RRR machines are designed to prevent a harmful amount of oil from mixing with the refrigerant during charging.

J2788H machines also do not contain oil injection capability, and this prevents the possibility of any type of oil being dispensed from the machine. If an older, SAE J2210 (or a “non-H” J2788) machine is used for conventional A/C systems, it cannot be used to recharge the A/C systems on hybrid vehicles that use an electrically driven compressor. However, there is a device whose use can permit an exception.

To allow the use of non-J2788H RRR machines on certain hybrids (and conventional systems as well), an add-on filter 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 with electric motor driven compressors.


About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues.
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One Response to Use caution when recharging A/C systems on hybrid vehicles

  1. ishaq says:

    what is the high side prasar

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