Hello,
I've read a lot of posts about getting the A/C working on the Gen 3 ECMs, but only ended up more confused. This isn't my first go at A/C, and I got everything working well on an older Gen 3 ECM (Blue/Red), but can't get my P59 ECM (Blue/Green) to trigger the A/C relay when I turn the A/C on. If I go into HP Tuners scanner and manually turn on the compressor relay, everything works as should, compressor engages, if temp is over 200* fans turn on, idle doesn?t stumble. I know that my P59 used Serial Cycling originally, but setting this to any other setting made no difference, Analog, Analog Cycling. I am trying to trigger at idle with 12v to C2 17, and ground to C2 55 and have tried both the +&-, only + and only -. The only thing that seemed to make a difference was when I switched type to Passive, I could no longer trigger the compressor relay manually. I never tried "Not Fitted". I don't have any pressure sensor(s) connected to the ECM, but have a binary switch in-line with my 12v request signal and I am getting 12v through this switch. Under the tab, System-A/C-Hardware-Recirculation Fitted, I have that set to Fan #2 but tried AC Recirc as well. Setting that to AC Recirc, I was no longer able to turn on my #2 Fan from the scanner.
I'm at a loss as it seems others have gotten this to work, am I missing something? I'd hate to resort to a trinary switch to control fans and not have any bump in idle or RPM deactivation. This is a stand-alone setup, originally the ECM vehicle was a 2003 Yukon 6.0, only big change was I segment swapped to 4L80. OEM type compressor, 10S17F Four Seasons 78377. The only thing I can think of is, reading the post "A/C request Blue/Green connector ECU" at ls1 tech, I need to add the three-wire sensor (GM 13587668) to the high side refrigerant line. I can't see needing to add the two-wire sensor (GM 89040362) as this just adds/removes ground to the HVAC module, which I don't have. I'm monitoring in the scanner, A/C request, A/C Active, A/C Clutch Engaged, and A/C Disable (pressure). I never get A/C Request to go to yes nor get A/C Disable to go to yes, so is the 3-wire sensor still needed since it doesn't appear to be pressure stopping it from engaging? Manually turning on the compressor will get A/C Active and A/C Clutch Engaged to go to yes , but A/C Request and A/C Disable stays at no . Any help is greatly appreciated! Brendan