AC Relay Ground
Thread Starter
1st Gear
Joined: Jun 2008
Posts: 1
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AC Relay Ground
I have a 1996 and the A/C relay is not getting a ground from the ECM. If I manually ground the grond wire, the compressor kicks on with no problem. Does nayone have a simple fix, other than to rebuild my ECM?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Best to scan it to see if it's getting an a/c request from the Processor or A/C Programmer first. Here's how it works: You press the a/c button on the dash controls and a digital signal is sent to the Programmer over a Serial Data Line (and an open in that line is rare). And the Programmer will send that signal to the PCM as long as no a/c trouble codes are recorded or set. The PCM then grounds the Relay as long as the Pressure Sensor is showing somewhere in the neighborhood of .8 volts but less that 4 volts (about 80 psi but less than 400 psi of system pressure) and will keep it grounded as long as the pressure sensor signal rises (not above 4 volts or 400 psi) when the clutch is engaged. If you don't have a scanner (which is the preferred method because it's the best way to see the Pressure Sensor signal and a/c request), you can at least check it for a/c trouble codes. Go here: https://www.corvetteforum.com/techti...=193&TopicID=2 You can also post all the data you get and we can tell you what it means. Finally, you can clear any glitches in the Programmer by removing memory power or simply disconnecting and reconnecting the battery. Sometimes, that gets it going again.
