2000 Corvette A/C inop and engine overheats in traffic

mchan68 · May 27, 2015

Not sure where to put this, so hear it goes. A/C Freon has been confirmed, charged to spec but does not operate. When I attempt to select A/C, the indicator on the HVAC control only flashes and doesn't come on. I've checked it for DTCs (using my own generic scan tool) and it comes up with no DTCs (PCM). The temp gauge does move up to 3/4 of the range, and while monitoring ECT the hottest I've managed to get it up to, is 110*C. I have a feeling the two concerns are one in the same, because the cooling fans don't come on. Accelerate up to speed, and the ECT drops to 98*C. I've pressure tested the cooling system with no leaks or pressure drop found. Anyone have any further information to offer before I tell the advisor to ship it to the GM store next door?

ktmlew · June 2, 2015

You need a scanner that will communicate with the BCM.

mchan68 · June 2, 2015

Funny you mention that. I did manage to get codes to display in the odometer window by pressing two buttons (don't remember which two). One of the codes displayed was U1096 if I remember correctly. But disconnecting and reconnecting the battery restored A/C and cooling fan function. Driving it around a little bit, and I was unable to get the symptoms to reappear.

8WA Sman · June 3, 2015

Besides testing the battery, diagnosing a Corvette communication problem without the proper scan tool is almost like trying to work on a 6.7 with the Star tester

mchan68 · June 10, 2015

Okay, this one is back. The A/C and cooling fans were still functioning at this point. The customer claimed the gauge moves to 120*C in stop and go traffic. Well, on road testing this unit, the highest I was able to get the gauge to register to, was 100*C (212*F) which seems perfectly reasonable to me. It's only when it is stopped, and revved up to about 3500 RPMs in neutral is when I get the gauge to register up to about 110*C, but the fans are already on at this point, so releasing the throttle moves the temp gauge back down to approaching 90*C. Surmising it might possibly be a gauge reading issue (as opposed to overheating issue), I call an ECT with no guarantee of a "fix".

Replace the sensor, and running the vehicle outside at 3500 RPMs now does put the gauge up to 110*C and a little bit above, with coolant bubbling in the degas bottle. What gives? :banghead: It gets better. Put the A/C on, and now it quits working again, with the HVAC displaying -8*C for outside temperature. And the kicker is, the cooling fans are still running (which they weren't before when it came in with the original concern).