[Cerberus]

So, I tried searching for this but I honestly do not know how to even go about it. Every search term I tried came back with 0 results.

Today, on the way home I popped through the touch less car wash. Shut the car off, start it at the end and the AC spools up than shuts off. Outside temp display is reading -21*F. My initial thought was the censor was close to an AC line and just purged all the refrigerent out. I had to get gas, shut the car down. Restarted problem persisted. Ultimately I messed around with different settings, manual, auto, fan speed, blower direcction and all of a sudden the gage started creeping up and once it got to about 40F the ac came back on.

So I am glad it "fixed itself" but I am wondering if this is an issue someone else has had and is it a sign for a future failure or some kind of persistent issue?

irok

your coolant temperature sensor lost signal.it defaults to -20 if unplugged and AC is designed not to come on at these low temps.check to see that harness on sensor is properly connected.sensor on driver side of engine below alternator.

Fly N Low

Dano523

My guess, either a bad connection at the temp sensor at the radiator, bad connection on the controller connector, or just a cold solder joint on the controller board that has to be re-soldered.

If you where stationary when you where playing with the controller buttons (no jolting back up at the rad sensor), then suspect that the problem is the controller connector or controller itself.

One last thing and set the DIC to voltage and drive the car around for a while monitoring the cars voltage. If the voltage drops below 13 volts, then it could be a charging problem/voltage making it way back from the engine fuse box to the modules in the car, with the voltage to the modules dropping enough to glitch/low voltage the modules to cause the problem isntead.

Hence with the car idling and the A/C shut off (third button on the controller from the left should have the following voltages when check with a multi-meter,
Alternator body to the terminal on the back of it under the rubber boot, 14.7 volts DC.
Battery on its terminals, 14.5 volts.
engine fuse box terminal positive, and both the battery terminal ground, and body of the alternator as ground, 14.5 volts.
DIC in the car set to voltage, 14.1~14.3 volts. Note, DIC is telling the voltage at the ECM, which if voltage from the engine fuse box, to the BCM, then to the ECM. Its not telling you the voltage at the dash gauges.

If you get your hands on a Tech II, then you can check the voltages of the rest of the modules (including the dash gauge), which should have the voltages at 14~13.8 volts DC starting with the BCM outwards. If any of the module are below 13.4 volts, then you have a problem with the voltage to that module. Again, power to them is coming from the BCM to start with, so could be problems in their wire connectors from the BCM to them, or could be a problem is that modules ground point instead.

Hence my first check on any vet with electrical problems, is to first check the voltages of the entire car, so I can weed that out to start with.
In your case its the HVAC controller, and so long as it reading above 14.4 volts, we can weed out it not getting enough power to start with. So at this point, quick check of the connectors of it and the temp sensor at the rad to make sure they are clean and making a good connecting, then pulling the controller to get to its board for a quick check for cold solder joints that may need to be re-soldered next.

[Cerberus]

Thank you for the replies, yes it was the ambient outside air temp display on the climate control screen. I assumed it might have been a bad sensor, since it shot right down to a low negative but I have issues with the climate control in my silverado so I did not know if the Chevy curse struck my car. I did just recently have the engine out this spring, so maybe that connection is a little suspect and it got hit by the under spray jets. .

I was driving while I was messing with everything, so now I am not sure if it was me just going through screens, or if a bump knocked the connector back and it started reading again, I will check.

irok

yes but even then AC won't function