P04 AC Min Air Temp parameter

[rjdrew1986]

Universal Patcher has a variable identified for the P04 PCMs called 'AC Min Air Temp' (please see attachment) which on the surface appears that it would help an issue on P04 GM's with the automatic climate control. The issue with the automatic climate controllers is anytime the RECIRC button is pressed, the AC compressor is switched on. The only work around is to press the vent button. So, this leaves (2) undesirable options in cold weather, either combat chilled air from the AC compressor or from the outside.

When I try to adjust this parameter, it seems to be acting in reverse of what is expected. When the air temp falls below the parameter setting, the AC compressor is enabled. I was hoping to be able to disable the AC compressor when the air temp falls below the parameter setting thus not chilling the air when its cold outside. Can anyone shed any light as to what could be causing this reverse acting affect and possibly how to work around it. The parameter works, it just seems backward, Note: Just ignore the shown -40C, this was a screen capture that I happened to grab as I was experimenting with the settings.

P04 AC Min Air Temp parameter .jpg

[rjdrew1986]

The 2003 Buick LeSabre mentioned (above) came with a Serv Nbr. 12583826 / HW Nbr 12582721 (P04) PCM. Starting in 2004, GM changed the PCM to a Serv Nbr. 12583827 / HW Nbr 12582720 (P04) PCM. I cannot find any definitive information as to what actually changed. I stayed with the original Serv Nbr. 12583826 / HW Nbr 12582721 (P04) PCM and loaded the program (Full Flash Clone) from the newer Sev Nbr. 12583827 / HW Nbr 12582720 (P04) PCM and now the 'AC Min Air Temp' parameter works perfectly as expected (when air temp falls below the 'AC Min Air Temp' setting, the AC compressor is disabled. And by moving the original calibration over, the car runs the same. I can only assume that there was an error in the 'AC Min Air Temp' in the Serv Nbr. 12583826 O.S. code (the OSID was different). A special callout to Kuro for exposing this parameter in Universal Patcher, I don't think this parameter was exposed for editing in the HPT, EFLive or Jet software. At least now my AC will be disabled below a certain air temperature.
Can anyone shed any light as to what changed between the Serv Nbr. 12583826 / HW Nbr 12582721 (P04) PCM and the Serv Nbr. 12583827 / HW Nbr 12582720 (P04) PCM?

[kur4o]

It may be just an updated version. You can check the update tree by VIN number online on delcotds site.

All p04 stuff came from tinytuner database, so all credits should go there. It may be some more parameters missing[incorrectly labelled on newer OS] or not complete database per the service OS number, but it is great you finally get it to work.

[rjdrew1986]

Thanks Kur4o. The only difference that I have been able to find is with the two O2 Heater circuits. The O2's used with the 12583826 heater resistance is about 5.5 ohms, the 12583827 O2 Heater resistance went to 11 ohms. The physical field wiring is the same and the O2 thresholds shifted a bit. I'm not sure what they were trying to accomplish. The good news is the min AC Temp logic works on the 12583827 OS.