Buick Regal A/C Dead: Compressor Won't Engage

Had a similar issue with my 2013 Buick LaCrosse last summer. As someone with some basic repair experience, I initially thought it was just a simple A/C compressor issue, but it turned out to be more complex. The symptoms matched yours exactly, no cooling, compressor not engaging. After taking it to the shop, they found the root cause was an electrical undervoltage problem affecting multiple systems, including the A/C pressure sensor and compressor relay. The repair involved: Testing the electrical system, Replacing a faulty pressure switch, Recalibrating the A/C system sensors, Checking the belt tensioner condition Total repair cost was around 240, including diagnostics and labor. The A/C has worked flawlessly since then. Before suggesting more specific solutions, could you share: Have you noticed any other electrical issues? Does the compressor make any noise when trying to engage? What exact error codes did your scan show? Has the car had any recent battery or alternator issues? These details would help determine if your issue matches my experience or points to a different problem.

After completing my latest service at 167659 KM, I discovered the root cause was actually a faulty relay switch in the HVAC system. The mechanic found that while the A/C compressor itself was fine, the pressure switch was sending incorrect signals, causing the system to shut down. The diagnostic scan showed error code P0645, which pointed directly to the A/C compressor circuit problem. A quick check of the belt tensioner and refrigerant levels confirmed these weren't causing the issue. Replacing both the relay and pressure switch resolved the problem completely. The total repair came to around 180 Euro, mostly labor costs since the parts were relatively inexpensive.

Thanks for the update on your Buick, good to hear you got it sorted out! Your repair details match what I suspected after seeing similar relay issues in these models. The P0645 code is definitely a telltale sign of the A/C relay problem. My LaCrosse had almost identical symptoms, though my initial diagnosis was off track. The pressure switch sending faulty signals is a known weak point in these HVAC systems. When the pressure switch fails, it often causes the A/C system to shut down as a safety measure, even when refrigerant levels are fine. Your repair cost sounds about right, actually a bit less than what I paid. Smart move checking the belt tensioner and refrigerant levels first, as those are common culprits for A/C system failures. Mine needed a belt tensioner replacement about 6 months after the relay fix, so might be worth keeping an eye on that. Did the mechanic mention anything about the condition of other electrical components while they were in there? Sometimes these relay issues can be early warning signs of other potential electrical problems.

Great news, I wanted to close the loop on my 2015 Buick Regal GS A/C issue. The mechanic checked out those additional electrical components you mentioned, and everything else in the HVAC system looked good. The relay switch and pressure sensor replacement totally fixed it. The belt tensioner looks fine according to their inspection, but I will keep monitoring it based on your experience. The A/C system is now working perfectly, good cooling and the compressor engages normally. Glad it turned out to be a relatively straightforward fix. Thanks for mentioning the potential connection between relay issues and other electrical problems. The diagnostic check showed all other systems are functioning normally, but I will stay alert for any unusual electrical behavior. For now, the repair seems to have resolved everything and the final cost was definitely reasonable compared to what I initially feared.