After the introduction of the 2nd generation, 2004+ Prius all Toyota and Lexus hybrids began using electric air conditioning compressors controlled by the inverter/converter.  By introducing these electric compressors they changed some of the service requirements for these hybrid air conditioning systems, specifically the oil used in the system and some diagnostic procedures in addition to a few extra precautions around the high voltage feed going to the compressor.  As Eden Prairie’s Toyota and Lexus hybrid specialist, we though we’d share some information on the unique needs of these high voltage systems as it relates to their repair and general service.

As the air conditioning compressor uses voltage from the high voltage traction battery to do its job, the compressor shouldn’t be handled by anyone other than a trained hybrid mechanic.  While unlikely, there is risk of serious shock or death when working on the compressor.

The new compressors require special oil to lubricate their internal moving parts while protecting the windings of the electric motors inside the compressor.  Toyota introduced their own special oil, ND-11, that meets both the lubricating requirements of the compressor and the dielectric, insulation protecting needs of the high voltage compressor’s electrics.  Here’s the ND-11 next to traditional ND-8 compressor oil:

ND11 Oil

Preventing cross-contamination of traditional air conditioning oils with the ND-11 during service is crucial to preventing premature hybrid air conditioning failure.  Certain equipment is designed to prevent this contamination like CARspec’s Robinaire 34788 when used with separate oil injectors:

Servicing Air Conditioning

If the vehicle is serviced with other oils or contaminated equipment, enough non-ND-11 oil in a Toyota/Lexus hybrid’s air conditioning system will short out the electric compressor.  This disables the system and can potentially leave the vehicle stranded (the vehicles sees it as a high voltage leak and can disable the entire system for safety reasons).  Ultraviolet dyes used to diagnose leaks are also not recommended – only Toyota ND-11 or equivalent compressor oil should be used on any electric air conditioning compressor.

What’s an owner to do if there air conditioning system was contaminated and the compressor failed?  Although rare, contamination requires replacement of all components including the condenser, dryer, compressor, expansion valve and evaporator, including the removal and cleaning of all hoses and lines.  Residual oil in these can cause repeated failures.  The hybrid specialists here at CARspec hope this helps an owner prevent a costly repair due to incorrect service of their air conditioning system!