Loosing AC, cruse control, engine temp and tach functions

[bentonbear]

I'm hoping for some advise on my 1990 Reatta faults. Seems like at any time the same four things happen at the exact same time. I loose the inputs for engine temperature, the tachometer, the cruse control quits, and the air conditioning quits. It's an intermittent problem. I've checked all the connections I could get to in and arround the motor compartment and fire wall and also up under the dash. I keep thinking it must be an electrical connection that has all four inputs in common or possibly the ECM. Any assistance / advise on this is much appreciated! Thnaks!

[Howard]

While I've never had this to happen, nor have I seen this exact problem on the board, I will state that I think indeed it is an electrical problem. It sounds like a ground issue. There are some "grounding" blocks mounted under the right fender that some people are unaware that they are there. They are above the battery area. Have you checked the connections at that point? Also, don't forget the battery itself. Loose connections or frayed wiring on the battery connections can wrack havock on electronic components.

[Barney Eaton]

The common link I see is both the ECM and BCM.

The cruise, tach and temp all go directly to the ECM then to the BCM, The AC clutch will not work without a ground signal from the ECM.

I would first try unplugging and replugging the three big connectors from the BCM behind the glove box. I would also do the ECM and you get to that from under the dash on the passanger side.

If that fails try finding a spare ECM and BCM from a wrecked Riviera and give that a try.

[bentonbear]

Howard / Barney. Thanks for the sugestions. I've checked the grounds with a meter and removed, cleaned and re-attached the battery cable ground. No improvement. I then removed all connectors from both the ECM and the BCM and re-attached them. No improvement here. Guess I'll start looking for someone who has a pair of spare modules. It's puzzeling that a module would have this type of intermittent problem. One would think it would keep working, or just stay broke. Anyway, Thanks again!