Page 17 - Summer 2018 GMC Vintage RVing

For additional technical presentations, papers, manuals, and other information go to gmcmi.comGMC Factory Air: Design and EvolutionK. Bradley | 1975 Eleganza | San Jose, CaliforniaAir conditioning is a perennial problem with our beloved coaches, and every year as the weather warms up, GMC owners try to fix it. GM recognized the failings back in the day and made considerable changes, eventually achieving an adequate solution. When trying to improve any system, it is helpful to understand what was there originally, what was tried in the past, and why.There were three major factory air versions produced by GM for the motorhome, referred to as “Type I” (1973- 74, early 75), “Type II” (late 75 through 76), and Type III (77-78). All model years used the same basic box to house the blower, evaporator, and heater core, though the interior design of the box varies. This large black steel box is mounted outside on the center of the firewall. It’s hard to miss if you look under the hatches.At this box, the blower pulls in outside air through a hole in the front cover and, on most models, can also take inside air via a vacuum-actuated “Recirc Door”. Pressurized air flows from the back of the box forward through the evaporator where, if the AC compressor is running, it isEvaporator/Blower HousingType ISUMMER 2018 GMC MOTORHOMES INTERNATIONAL 17