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a/c stuck on - ECM?

I've got a 96 K1500 Suburban. The a/c compressor compressor (clutch) is now on always when the engine is running. The a/c switch light on the dash toggles normally, but has no effect. The compressor clutch releases just fine when the wires to it are disconnected. The a/c relay is not shorted and works fine. It seems the relay coil is always energized by the ECM. This is where I lose it. Is there some way to diagnose it through the ECM? Do I need to replace the ECM? Where is the ECM? I have a Chilton manual with wiring diagrams, but I can't see how the a/c switch on the dash feeds into the ECM. Any help is greatly appreciated.

-Roy

Reply to
Roy Reichwein
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Inline.................

No.

Probably not.

Should be on the passenger side of the engine bay, either mounted to the inner fender or behind the firewall.

Try resetting everything first, by yanking the PCM fuses and leaving them out for a few minutes. It'll run like junk for the first few minutes after restart as it relearns everything, so don't freak out.

Doc

Reply to
"Doc"

Wow, that worked. Thanks a 1/2 ton!

-Roy

Reply to
Roy Reichwein

You're welcome.

Doc

Reply to
"Doc"

In regard to your successful solution:

"Try resetting everything first, by yanking the PCM fuses and leaving them out for a few minutes. It'll run like junk for the first few minutes after restart as it relearns everything, so don't freak out."

Would disconnecting the battery have accomplished the same thing?

Of course, disconnecting the battery used to cause a lot more work, like having to reset the clock and favorite ratio stations.

But would the battery disconnect work?

Reply to
One-Shot Scot

Inline....................

Yep.

Still does.

Yes, but he'd lose his clock and radio settings, plus if he had a Theft-Lock radio and forgot to disable it before yanking the battery it would need to be unlocked by the dealer.

On OBD-II vehicles, it's just easier to yank the PCM fuses.

Doc

Reply to
"Doc"

Reply to
One-Shot Scot

Reply to
"Doc"

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