AC & Temperature Gauge not working

[Envoy09]

Hi guys,

Since the last couple of weeks, I've having the below 2 issues on & off. These 2 issues ALWAYS happen together.

1. The AC doesn't work / cool, i.e. the compressor just doesn't kick in.
2. The temperature gauge doesn't work. Please see the attached pic. The engine isn't cold here. Pic is taken after driving 50km.

Any idea what this could be? Since these 2 issues happen together, I'm quite sure it has nothing to do with the AC compressor.

 

[Mooseman]

The two issues are not related. For the AC, if the compressor isn't working, then the system needs to be diagnosed to find the cause. The most likely is a loss of refrigerant. Also a possibility is a defective low pressure switch which is located on the dryer/receiver (the aluminum can on the passenger side firewall). As a quick test, unplug the switch and short the wires momentarily in the plug. If the compressor comes on, have the system checked for proper refrigerant level. If that's OK, then suspect the switch.

For the low temperature showing on the gauge, three possibilities. 1. The coolant temperature sensor is defective. 2. The thermostat is stuck wide open and over cooling. 3. The gauge's stepper motor is defective. You would need a scanner that can show live data and read the actual temperature from the PCM. If the scanner shows a normal temperature, then the stepper motor is defective. If it is low, then either the thermostat and/or the sensor are defective. These are usually replaced together due to their high failure rate. But the temperature being shown looks unusually low, even with a defective thermostat so I would lean towards the stepper motor. Does it move at all?

 

[Envoy09]

The 2 issues are definitely related. It's not that these 2 issues are there always....they happen once in a while. And when they occur, they occur together.

 

[Envoy09]

Can Admin please move this post to the Envoy section? I posted in Tahoe, Yukon section by mistake.