GMC Terrain AC Dead: No Cooling, No Compressor Engagement

I had a nearly identical issue with my 2016 GMC Acadia Diesel last summer. Having some experience with AC systems, I first suspected a refrigerant leak, but it turned out to be more complex. The symptoms were exactly like yours, no AC noise when engaging the system and complete failure to cool. After checking the obvious things like AC relay and pressure switch, my mechanic discovered defective valves in the air conditioning system that needed replacement. The total repair came to 1000 Euro, including parts and labor. Driving without getting it fixed risks damaging other AC components, so I would recommend having it checked soon. The lack of AC noise when engaging the system often points to electrical issues or valve problems rather than just a refrigerant leak. To provide more specific guidance, could you share: Are there any other unusual sounds from the engine bay? Did the AC gradually lose performance or fail suddenly? Does the AC button light up when pressed? Have you had any recent AC maintenance done? The issue might be similar to what I experienced, but these details would help confirm if were dealing with the same problem.

Thanks for sharing your experience. My vehicle has 59494 KM and was serviced last month. The blower motor seems completely dead too, no response at all when activating any temperature control settings. For your questions: no unusual engine sounds, the AC failed suddenly during a drive, the button does light up briefly when pressed, and I have not had any recent AC diagnostics or maintenance done. Based on your repair cost info, I should probably start budgeting around 1000 Euro for this fix. Would you recommend checking the AC relay first since its potentially a simpler electrical issue before diving into valve replacement?

Based on those symptoms, especially the completely dead blower motor and sudden failure, your issue sounds different from what I encountered with my Acadia. The blower motor working was a key distinction in my case. This actually points more toward an electrical problem rather than the valve issues I dealt with. The pressure switch or a blown fuse could be causing both the AC efficiency problems and blower failure. These are relatively simple fixes compared to the valve replacement I needed. Since your button lights up briefly, the control module is getting some power. I would definitely check the relay and fuses first, it could save you significant money compared to my 1000 Euro repair. When my AC noise stopped, the blower still worked, which was why we focused on the valve system. A quick diagnostic tip from my experience, check if you hear any clicking sound from the relay when pressing the AC button. That helped identify the difference between an electrical vs mechanical issue in my case. The lacking blower response in your case makes me think the root cause is different from what I experienced. Consider having the cooling system electrical components checked first. Unlike my valve problem, yours might be a much simpler fix if its relay or fuse related. The AC maintenance history being minimal also suggests this might be a basic electrical issue rather than a system component failure.

Based on the relay suggestion, I think I will try checking the electrical components first. I just looked under the hood and found the fuse box, will start there and with the relay before taking it to a shop. The complete lack of blower motor response and AC noise definitely makes me hopeful this could be a simpler electrical fix rather than a major valve repair like yours. Since my AC failed suddenly and all climate control functions stopped at once, an electrical issue seems more likely than a gradual refrigerant leak or valve problem. I appreciate the advice about getting it checked soon though, will have a shop look at it next week if the fuse and relay check doesnt resolve it. Looking at around 1000 Euro worst case for major repairs isnt as bad as I feared. Planning to document what I find with the electrical check in case anyone else runs into similar temperature control problems with their Terrain. Will report back on whether this ends up being a quick fix or if I need the full AC diagnostics treatment.