wkdivr Posted April 3, 2007 Report Share Posted April 3, 2007 I had my battery disconnected while I did some work to my truck this winter. When I get the truck running, I can't get the A/C to kick on. I can comand it on with HP Tuners, and it blows cold, so I know it doesn't need charged but it won't come on by itself. It's a manual system, when I push the A/C button, the indicator light comes on showing power to the system, but the compressor clutch doesn't kick in. My service manual mentions something about the HVAC system having "keep alive memory", but doesn't mention how to get it back. Anybody have some suggestions? Quote Link to comment Share on other sites More sharing options...
perk03z06 Posted April 3, 2007 Report Share Posted April 3, 2007 (edited) Well ... if you can command it with a scanner, then you definitely know that the A/C clutch is working. However ... I worked on a GM system w/ a buddy of mine & we were having the same problem you were having. But, there was one time we went to command the A/C on, and the response from the PCM came back "High Sensor Exceeded Threshold" ... so we went right for the High Side sensor ... and it was reading something like 192 lbs. of pressure with the A/C system OFF .... and it ended up simply being the high side wire that was shorted to ground. We patched that all up, and the A/C came on as soon as it saw the request from the dash. So ... in your case ... I would hunt around for wires that look like they've rubbed up against something, and rubbed the insulation off. W/o being able to take hi & lo pressure readings on your system, it's not easy to determine exactly, but it definitely sounds electrical ... and there's some kind of pre-condition that the PCM is looking at to be met before it engages the A/C compressor clutch. Good luck! BTW: Not sure about the HVAC modules having KAM (Keep Alive Memory) ... but if they do, Keep Alive Memory is nothing more than a few capacitors inside the module storing energy that gets used after the ignition key is turned off. This keeps the module awake after key off to handle other functions, if necessary. As far as "getting it back" ... not sure what you mean ... Edited April 3, 2007 by perk03z06 (see edit history) Quote Link to comment Share on other sites More sharing options...
Krambo Posted April 3, 2007 Report Share Posted April 3, 2007 My truck has electrical "bugs" and when I swapped my tranny, I had the battery disconnected for 2 months. When it was all buttoned up, my radio wouldn't work, my heat/AC (electronic) wouldn't work and my memory seats were all out of wack and wouldn't hold the program. I took it for a test drive (about 10 miles) and at least 10 start-up cycles and wouldn't ya know it, it all cam back to normal. I think it has something to do with internal micro-batteries / caps that become fully discharged like mentioned above. Quote Link to comment Share on other sites More sharing options...
wkdivr Posted April 3, 2007 Author Report Share Posted April 3, 2007 Well........it seems I found my problem. I must have unplugged my low side connector when I did the headers. Didn't notice it untill a friend said"what's this??!!" I get the dumbass of the week award!! Quote Link to comment Share on other sites More sharing options...
wody Posted April 3, 2007 Report Share Posted April 3, 2007 well at least it was something fairly easy and not too in depth. electrical can really kick someones ass. Quote Link to comment Share on other sites More sharing options...
Holty Posted April 4, 2007 Report Share Posted April 4, 2007 Well........it seems I found my problem. I must have unplugged my low side connector when I did the headers. Didn't notice it untill a friend said"what's this??!!" I get the dumbass of the week award!! Quote Link to comment Share on other sites More sharing options...
perk03z06 Posted April 4, 2007 Report Share Posted April 4, 2007 Well........it seems I found my problem. I must have unplugged my low side connector when I did the headers. Didn't notice it untill a friend said"what's this??!!" I get the dumbass of the week award!! Darwin Award! Quote Link to comment Share on other sites More sharing options...
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