Hybrid and battery electric vehicle A/C would start getting warm. The only way to keep the compressor working was to press the MAX A/C button, which forced the engine to run and took away from the fuel efficiency of the hybrid design (the primary reason customers want these cars in the first place). So in 2004 they converted to an electric compressor that allowed the A/C to keep running even when the gas engine wasn't, at least until the high voltage battery needed a charge. See Figure 2. Progression of the Prius Compressor: Image 2a Image 2b Image 2c Image 2d Figure 2: Early Prius models used belt-driven compressors until 2004 when electric scrolls became the norm. Take note that 2010 models changed to a 140cc variant due to system efficiencies gained through ejector cycle evaporators. 2000-03 2004-09 2010-15 2016- Denso SCS06C Denso ES18C Denso ES14C Denso ESB20C Belt driven scroll Electric scroll 180cc Electric scroll 140cc Electric scroll 200cc ND8 Oil ND11 Oil ND11 Oil ND11 Oil Prius also brought us some other A/C advancements, such as the ejector cycle evaporator. First introduced on 2010 models, it helps to reduce compressor power consumption by 11% at 77°F and up to 24% at 104°F, directly improving fuel economy. It works by using a specially shaped pipe with no moving parts that produces a pumping action as the refrigerant flows through and produces a pressure rise that represents recovery of the work that the compressor performed (Figure 3). Figure 3: Ejector is a piece of specially shaped pipe with a tapered inlet nozzle. Notice the reference to "secondary flow from evaporator." That is just one part of a dual evaporator assembly. At the far right end of the ejector pipe, following the "diffuser," is where refrigerant flows into a primary evaporator. 20 ACTION/NAPA * Spring 2017