A/C Unit stops working on hot days
 

Have any of you had the same issue I am having? On my 2006 vehicle (S40), the A/C works 80% of the time. However, on really warm days, there are prolonged periods where it will only blow out warm air. My mechanic took a look at it (handles different types of European vehicles), and didn't know what to do short of replacing the entire A/C unit. Is this a computer glitch or something mechanical. On cold days, the A/C unit works all the time. Thanks!

Probably need a compressor clutch. Very common.

That is also a symptom of slightly low freon. The system may be able to condense freon at 90 degrees F but not 95.

Either of these two issues would be extremely easy to diagnose at an A/C shop.

Thanks. My local mechanic checked it out, but it's been cold lately, and he didn't see any issues. When it gets warmer (and I know this problem with the A/C will arise again), am I better off taking it to a Volvo S40 dealer or a local A/C shop. I'm guessing its the compressor clutch, since I've already had the freon checked. Great advice though. Thank you!

you can just look at the clutch and see if the compressor is running or not. You don't need to take it anywhere for that. You need to see it turn on at least once to know what that looks like.

If the clutch gap gets too wide, the clutch will open up when it heats up. depending on your model, you can reshim the clutch to narrow the gap. But as noted you should check the system pressure first - (using the pressure appropriate to the ambient temperature... and measure while the AC is running)