Delphi Dave Hobbs Dave Hobbs Figure 8: The EOAT (Evaporator Out Air Temperature) in this logic chart is the sensor helping the HVAC controller to supplement the pneumatic control of the variable displacement compressor with a little cycling now and then when cool air is more cool than needed to achieve fuel-saving Series Reheat Reduction. cooling performance during idle stop. Just keep the gas engine running so I don't have any idle stop; I don't care about MPG, I care about staying cool!" In some cases, it may be an HVAC related button marked Econ which makes you ask yourself, "Won't this prevent compressor operation?" In the case of hybrids and many new vehicles supporting 12-volt stop / start systems with advanced HVAC compressor management, the answer may likely be NO. Regardless of which vehicle your customer has, make sure whenever addressing HVAC cooling performance OR fuel economy complaints that you know how the vehicle should work and then pass that information along to the customer to make sure a problem actually exists with the vehicle or if the problem is in reality a lack of education on vehicle operation. A bit of tutoring your customer with their vehicle's owner manual can repair a lot of vehicles! See Figures 9 & 10. ■ Figure 9: Green means Eco, as in allow the EOAT sensor to see a few more degrees than desired prior to commanding the gas engine to discontinue idle stop (restart) so the belt driven compressor can run and cool down the passengers again. This enables idle stop for longer periods. Customers will notice a little less A/C performance at idle as the evaporator warms up without compressor operation. August 2015 Figure 10: The amber LED displays on the second press of the A/C request button to tell the HVAC that you don't want better fuel economy, you want better A/C cooling! 6 MACS Service Reports