Bird

iTrader: (25)

98 SS - the A/C will not come on. Freon level is correct and all fuses are good - I know that it's effectively PCM controlled, but all inputs to the PCM are good and it still will not turn on. Can go in with EFILive diagnostics and tell the PCM to turn on the A/C and it will work perfectly, but when it has to decide by itself, it will not turn it on. Checked the A/C request, hi-pressure signal and ECT - all good.

Almost seems like the PCM is going bad in that circuit - anyone have any ideas?

Bird

BLK02WS6

iTrader: (2)

I think you are over-riding something doing it that way (I'm thinking pressure switch)... if the tune hasn't been tampered with, it really shouldn't be anything in the tune. And if it was wiring related, you wouldn't be able to turn it on with EFILive... I'm thinking the pressure switch may be the issue. Might wanna search some diagnostics online for the A/C system.

Bird

iTrader: (25)

As I said in the previous post - ALL inputs check out good, including the hi side pressure - the override through EFI live was just to test the output circuit of the PCM through the compressor relay to the compressor. Datalogged the ECT and the hi side pressure and checked the A/C request signal into the PCM - all are good and no DTC's that would cause the PCM to not turn on the A/C.
Nothing has changed in the A/C control of the tune since it last operated properly.

Bird

hwoods864

I am having this same problem but did not see a solution...

2002 PCM

Measuring the voltages at the PCM connector, I have 12 volts on the A/C request line going into the PCM and 4.35 volts from the trinary switch into the PCM. The PCM will not enable the output (take it to ground) on the clutch relay enable.

Any advice would be appreciated.

jimmyblue

iTrader: (11)

If it works at cruise but not at idle, check that the "stall
saver" stuff is not inhibiting the A/C for "unsteady idle".
Part of that "strategy" is not letting the A/C turn on if
the idle is having trouble.

hwoods864

Thanks. I had seen somewhere that the PCM would turn off the A/C if it detects an unsteady idle but nothing that said that it would not turn it on, though that makes sense as well.

Unfortuantely I am not in a situation where I can drive the car in a way to test the theory. I am building a Factory Five GTM and while it is driveable, it is nowehere near where I can drive it down the street far enough to see if the A/C comes on (no body etc.).

It does idle pretty rough right now, not sure if it is the cam in the new LS6 or just being out of tune. It will be a few months before I will be able to get it back on the dyno to see if I can get the engine to smooth out so I guess I will have to wait and hope that will solve it.

Thanks again for your help.

Bird

iTrader: (25)

In my case, the stall saver was zero'd out - swapped the PCM, loaded in my tune and all was fine.

Bird