Most likely the compressor clutch needs to be reshimmed.

I am having the same issue with my s60 recently. It only happen on a hot afternoon randomly. When it happens I have to switch the a/c off then after 2-3 mins on it back again, the a/c works fine. When the a/c is blowing warm air the air compressor is being cut-off by itself because the electrical circuit to the magnetic clutch is broken which I have confirmed using multimeter showing no dc voltage across the wires terminal at the compressor. I suspect the cut off is due to high pressure on the a/c line. By the way where is the high pressure switch of the a/c system? The fan motor is working well when it happened. Any ideas what cause it.

The high pressure switch is on the dryer hidden behind the front bumper.

I have this problem too on my '95 850. Sounds like you're planning to replace or bypass your high pressure switch. I think I will try bypassing it to see if that stops the cutoff after 5 minutes.

Tech, how do you that? I think we have the same problem with our second car, compressor works fine for first 3-4 minutes after start up and then just stops.

I was wondering the same, and is this a job that can be done in a home garage or does it require disassembly of the compressor. Is the easiest job just to replace the clutch assy.... and if so can it be done with basic garage tools?

A .pdf of the parts involved (including the shims noted above) would be quite helpful.

Thank you for this great forum and the great advice.

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Nope... your compressor probably needs shimmed (or de- shimmed, as the case may be.) The trouble with the compressor not switching on is usually intermittent, and manually jumpering things often allows slightly more current to get to the clutch, which may make it engage when otherwise it wouldn't. Basically, what happens is this: with wear, the compressor clutch plate gets to be too far from the pulley to engage. This especially happens when the compressor is warm, because that air gap is larger due to thermal expansion. Shim the compressor clutch, and it should fix the problem.

To do this: there's a bolt in the center of the compressor clutch plate. You'll need some kind of tool to hold the plate while you loosen that bolt. often a screwdriver placed between one of the pins and the outer triangular plate will work. There's also 3 holes in the center of the clutch plate that you can rig something up to do this (or get the proper holding tool, which uses those holes) Once you've removed the bolt, rock the plate back and forth until it comes off. Sometimes some prying is also necessary- but be careful not to bend the clutch plate. In extreme cases, you'll need to use a puller, which will require removal of the compressor. After the plate is removed, you'll notice that there are 1 or more little washers in the hole where the plate attaches to the compressor shaft. You shim it by adding and removing washers of varying thicknesses. Usually, you remove one, and replace it with a thinner one or stack of thinner ones to solve this problem. The air gap between the plate and pulley should be .012"-.020" (.3-.5mm) when checked with a feeler gauge. The shims are available from the dealer, as well as automotive A/C and radiator specialty shops (there's an excellent company in Columbus, OH and in Louisville, KY called Roppel industries which carries all kinds of esoteric A/C parts and tools.) The shims are available from Volvo in the following thicknesses: .2mm, .3mm, and 1.0mm Install the correct shims, check the air gap, and reassemble.

thanks carrots
So, once I have the car on the lift I can actually get this done without taking compressor off unless its not coming off easy and requires using a puller? Very good news

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Would this diagnosis and remedy also hold true for a 1999 C70 experiencing identical issues?

Thanks!

Chris

I had the same problem with my V-70 XC: In hot weather the AC runs for a while then the cluth disengages and won't re-engage unless I shut the system off for a few minutes,. Then the same scenario occurs again. Normally I would have researched the issue first but I was in such a hurry that I just took the car to the local Volvo Dealer. The Service Writer said the Compressor was bad but couldn't explain what was bad in it. I thought there was either a high pressure or temperature cut-out swith in it but I only found the connection for the magnetic clutch. I had never seen this failure mode before so I went with their recommendation. $1300 later the A/C works fine but now that I have researched it I am kicking myself as I could have repaired this myself for $0.00! It pays to consult the Volvo Forum before taking the car to the dealer!

Greetings All, new guy to the forum. My wife has an XC70, 2001. Air conditioning keeps on cutting out in hot weather. I have removed the charge and made sure it has the stated 2.17 lbs of 134a, ( I am an air conditioning technician by trade). If I am reading into the postings correctly, the cooling fan is variable speed or two speed. This fan seems quite constant to me and runs slow, slow enough that the system may be shutting off on a high discharge pressure condition. What should I be checking for?? Thanks. Jon

Did you read posts #2 and #8 of this thread? Have you ckd the clutch shimming clearance?

As far as the fan in front of a/c condenser, if it's same as mid 90's 850/S70 it's not two speed (what makes you say that?) and if it seems like it's running slow it probably needs replacement; they're pretty loud when running.

I have the exact same problem on my XC70. I have had the pressure and temperature sensors changed and the compressor was checked and is okay.. What exactly did you have done to fix it and what was it you think you could have done yourself? We're hitting summer here again and I'm desperate as neither the dealership nor my aircon specialist have any idea

As other have mentioned in this thread - The common cause of "ac stops being cold after driven for a while when hot outside" - is a worn ac clutch. If the gap gets too large the electromagnet can't keep the clutch engaged. So - you usually can remove shims o make the gap correct.