Audi SQ5 A/C Compressor Failure, Complete DIY Guide

Had the same issue on a 2020 A5 with similar symptoms. The AC relay was the root cause, preventing power from reaching the air conditioning compressor. Initially thought it was the pressure switch, but diagnostic tests revealed an undervoltage condition at the HVAC system control module. The repair involved testing the relay switch circuit and replacing both the AC relay and a faulty pressure sensor. The compressor itself was functioning correctly, but the safety systems prevented it from engaging due to the control circuit issue. This was a moderately serious repair that required specialized diagnostic equipment to pinpoint. The pressure switch replacement was necessary because it was sending incorrect readings to the control module. After fixing both components, the air conditioning system returned to normal operation. If your error codes point to the compressor, start by having the relay and pressure sensors tested. The HVAC system often shuts down completely when these components fail as a protective measure. Getting a proper diagnosis from a shop with Audi-specific diagnostic tools is crucial for these electrical issues.

Thank you for sharing your experience. I am also dealing with an A/C system failure in my SQ5, and your relay switch solution caught my attention. Did the repair last, and do you remember the total cost? Also curious if any other components of the HVAC system needed attention since the initial fix.

After getting the undervoltage issue fixed at the shop, my air conditioning has worked flawlessly. The complete repair, including diagnosing the relay switch and correcting the voltage problems in the HVAC system, came to 240 Euro. The mechanic confirmed the A/C compressor shut off was happening due to the safety systems detecting low voltage, not because of a faulty compressor. No other components needed replacement since the initial repair. The belt tensioner and other mechanical parts were all checked during diagnosis and found to be in good condition. The pressure switch readings returned to normal once the voltage issue was resolved, saving the expense of replacing those components. The key was finding a shop that properly diagnosed the electrical system rather than jumping straight to expensive compressor replacement. Based on your description, you might be dealing with a similar electrical issue rather than mechanical failure.

After reading the helpful replies, I took my SQ5 to a certified shop last week. The technician found that the pressure switch was indeed faulty, causing the A/C system to shut down as a safety measure. They also discovered a small refrigerant leak near one of the connection points. The total repair came to 380 Euro, covering the pressure switch replacement, fixing the refrigerant leak, and recharging the A/C system. The A/C compressor itself was perfectly fine, just as others suggested. The whole job took about 3 hours, and I am happy to report the air conditioning is now working perfectly again. This experience taught me the importance of proper diagnosis. What initially seemed like a major compressor issue turned out to be a relatively straightforward fix. The shop explained everything clearly and even showed me the faulty parts.