2006 Volvo S40

You haven't mentioned whether or not it is automatic temp control-meaning you set the temperature. If you haven't stil replaced the battery a low battery will cause all kindso fo screwy things to happen toyour car, driving or different sensors. Unfortunately you have a couple of different relays as well as a module of which any of them could be bad as well as any type of actual a/c freon type problem. This will need to be checked out unfortunately and will probably need to be scanned to see if there is some type of electrical problem like a relay/module etc.

The electrical system is similar on both units. Unfortunately you'll have to have a computer hooked up to see if they can find any codes causing th problem it may be just a bad ground or dirty ground causing the problem. It can still be one of the relays and going to the dealer the mechanic may know which one goes bad all the time. I know prices aren't cheap at the dealer and an intermittent problem like yours are not easily diagnosed. On the left side of enginge compartment there are 7 fuses you can check, they will be marked and see if they are bad. You will ve able to tell when you pull them out. There is also a climate control relay there which should be marked, you can pull that out and put it back in as they sometimes get dirty. The inside cover should have which fuse is which as well as which relay is which. That is something you can do if you don't mind getting your hands dirty. They may pull otu hard however.

Your most likely fault will be a worn compressor clutch. Very common problem on this vehicles and have been doing a few this summer LOL. Measure the gap clearance. Should be between 0.3mm and 0.5mm so if you can insert a feeler gauge greater then that you can remove a shim to bring the gap in closer or replace the clutch if you can not bring it back into spec. What happens since the gap is wide as the clutch gets hot the gap gets wider and the magnet cant pull it back in because the clutch is so far away when it cycles off and then back on again. And it is very noticeable in the summer time. Good luck to you and let us now what happens.

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