Alfa GT AC Dead: Relay vs Compressor Failure Guide

Had the same issue on my Alfa 159 2.4 JTD from 2008. The A/C system completely died without warning. After checking, it turned out the relay switch was fine, but there was an undervoltage problem affecting the air conditioning compressor. The main symptoms matched yours, no response when pressing the A/C button and error codes showing up. The issue turned out more complex than just a faulty relay. The belt tensioner was worn out, causing improper drive to the A/C compressor. Additionally, the pressure sensor had failed, which is a common weak point in these Alfa models. This was a serious repair requiring several components to be replaced. The pressure sensor replacement was necessary before the system could be properly diagnosed and recharged. The belt tensioner replacement was crucial to prevent future compressor damage. From experience, better get this checked soon. Running the car with a malfunctioning A/C system can lead to more expensive repairs if the compressor gets damaged. Common symptoms like these often indicate multiple failing components rather than just a single part.

Thanks for sharing this info. Dealing with similar issues on my GT right now and good to know about the pressure sensor being a common problem. My mechanic already mentioned something about the belt tensioner but wanted a second opinion. Did you remember roughly what the full repair ended up costing? Also curious if youve had any other AC related problems since getting it fixed?

Took my GT to a qualified mechanic last week and got everything sorted. The AC relay and HVAC system are working perfectly now, no more issues with the compressor shutting off unexpectedly. Total cost was 240 Euro to fix the undervoltage problem that was affecting the A/C system. It turns out diagnosing the pressure switch and refrigerant leak spots made a big difference. The mechanic did a thorough check of all AC components and found the voltage issue was preventing proper operation. Much cheaper than initially expected, especially compared to replacing the compressor. No problems at all since the repair. The AC blows consistently cold now and the compressor engages smoothly. Getting it fixed quickly probably prevented more expensive damage. Regular maintenance checks of the A/C system are worth it to catch these issues early.

Thanks everyone for the insights. Finally got my car back from the shop yesterday. The mechanic found multiple issues, a faulty pressure switch and a worn belt tensioner that were causing the AC problems. The diagnostic test also showed low refrigerant levels in the A/C system. Total repair came to 480 Euro including parts and labor. More than I hoped but less than I feared after reading about potential compressor failures. The AC relay itself was actually fine, just needed the pressure switch replaced and the system recharged. Drove around today and the AC is working perfectly again, nice cold air and the compressor engages smoothly. Really glad I got it checked out before any major damage occurred. Will definitely keep up with regular maintenance from now on to avoid similar issues.