Toyota Techstream enables you to perform active tests on the HV A/C compressor.
Have you looked under the hood of a hybrid vehicle lately? If you have, then you already are familiar with the fact that there no longer is a serpentine-style drive belt to turn the accessories. Perhaps you have seen the advertisements that on some models of hybrid vehicles you can control the climate control system from your smartphone. Things definitely are changing.
Hybrid vehicles have pushed engineers to rethink the way they design A/C systems. While they maintain many of the same components that we are familiar with, quite a few new components and diagnostic procedures have emerged. Traditional testing methods might not apply to hybrid A/C system diagnosis, and we as technicians need to get up to speed to keep pace with technology. In this article, we will take a look at hybrid A/C technology — and discuss repair and diagnostic strategies so you are well prepared when a hybrid A/C job comes through your bay doors.
A look at the differences
A high voltage A/C compressor is identifiable by the orange wire loom. Image courtesy of Denso
One of the major component differences in hybrid A/C systems is the design and control of the compressor. Early hybrids, such as the first-generation Toyota Prius, had a belt-driven A/C compressor. The strategy here was simple: If you turned the A/C on, then the engine had to run.
The compressor turned at a rate of speed determined by the engine speed and compressor clutch engagement, no different from traditional A/C systems. This worked well, but the mpg rating suffered considerably anytime the A/C was on.
With high demands on manufacturers to raise the mpg rate and improve battery life, unnecessary loads on the engine had to be removed. The problem this presents is that a belt-driven compressor cannot meet the need for A/C, especially if the engine is turned off.