Bought my C5 in January and today was the first truly warm day in Pa. I already knew the AC didn't work but today I was able to run it while the car was running to see if I felt even the slightest bit of cold air.

Nothing but warm air.

When I hit the AC button, I don't even here the engine idle change so I don't think the compressor or fans are even activating.

I have zero idea how this system works so can you guys help me start to diagnose the issues? What should I visually and audibly check for first? And what are the likely mechanical culprits?

Some additional information:

The heat seems to work fine. But the vents blow much stronger when the temp dial is turned to the cool vs hot setting.

This is a base model without the fancy hvac display.

Any help is appreciated.

 

First check to make sure the compressor isn't coming on. It could even be a broken or missing AC belt as it's a separate belt to the main drive on these cars I believe. If it's not coming on check fuses/electrical connectors. If everything electrical checks out then get a set of manifold gauges and check pressures. Autozone has them as a loaner tool and they will be much more accurate than the cheap gauges that come with r134. If you're too low for the compressor to come on, then you likely have a substantial leak that will need to be fixed.

I had a small leak from the low side valve that was causing my AC to get warm. I got new valves, pulled vacuum on the system to ensure no further leaks, and recharged the system with the correct amount of oil and r134. It CAN be done with stop leak, but a true fix is a much better idea.

Manifold gauges and a vacuum pump can be gotten as loaner tools from Autozone, if a leak is your only problem you can add dye and trace it, fix it, and refill using the manifold gauges you borrowed and a few cans of 134.

I dont recall if these cars have an expansion valve but if so it can get stopped up too, causing issues as well. I wouldn't worry about that at first though, check the other things beforehand. Also keep in mind that AC systems are finicky, more isn't better always. Often they should be left to professionals.

 

I don't think the compressor will engage if it is low on coolant. I'd start there.

 

That was my thought, too. Fill it up and add some leak detector and hope for the best.