90 reatta no ground to ac relay

Asked by GuruNHSQ Apr 27, 2017 at 05:16 PM about the 1990 Buick Reatta Coupe FWD

Question type: Maintenance & Repair

have a 90 reatta with a service ac light recharged it to spec still light checked
power at ac compressor no ac power checked ac relay found to have power
at the relay but no ground from ecm need help

1 Answer
10,490

txbarney answered 7 years ago

The ECM supplies that ground and trying to discover why the ECM is not giving the ground is a long process, if you can get your hands on a different ECM that may solve the problem. The ECM is for the engine and I suspect that any 1990 GM car with a 3800 engine would have a ECM that will work. Once you find one you can plug it in without pulling the original (the ECM is in the passanger footwell and you can pull the connectors without pulling the unit, then plug the connectors into the replacement and let it lay on the floor while you check out the operation. If the replacement works (makes the A/C relay turn on ) then when you pull the original, switch chips and recheck again.

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