Hi,
I am trying to avoid further diagnostic costs and misguided solutions from my mechanic with regards to my A/C compressor cutting out on me and blowing warm air.

Here is what happens: when the outdoor temperature exceeds 85 degrees, my car's A/C will stop functioning after about 20 minutes of driving time. If the temperature outdoors is not very hot, the A/C runs perfectly cool the entire time, and the compressor does not stop working. I have successfully driven for over an hour in cooler temperatures with the A/C on, no problems with cold air coming out of the vents.

I have recently had the A/C charged and the system was checked for leaks. No leaks, and it is now full of new coolant. Also, I have an 18 month old alternator, the previous was replaced due to failure. I don't believe my alternator is failing, but I cannot be certain until it's tested. On that note--is a weakened alternator likely to cut out the A/C in order to maintain its required amperage? The previously failed alternator did not fail outright, it was pushing 12.8 amps rather than 13.5. Over time (30+ minutes), the car would completely die. It was a difficult diagnostic since the previous mechanic didn't realize the partial failure of the alternator.

My other thought is the compressor is failing. How can I better diagnose this problem in order to avoid further unsuccessful trips to the mechanic in the next couple of weeks?

cpv,

It's probably the expanded gap not letting the electromagnet engage the clutch and either the easy shim or the "proper" shim project will fix it.

FWIW my '98 S70 exhibits the same symptoms and I have been able to add a couple of oz's of NAPA's snake oil mix of R134a/PAG oil/O-ring conditioner every other year to make it though the 90º+F days with no problem.

Anyway, either the $1.00 fix or the $3.00 fix (6 doses per can) seems like a reasonable price to keep a 10+ year old ac system going.

Good luck.
Bryan

Clutch gap!!! I agree with eveyone else.

I just performed the "bread clip" fix on both a 98 S70 and an 00 V70. Both of them were exhibiting identical symptoms to those you describe and both are working perfectly now.

See Klaus's post with the link.

It takes 20 minutes and is easy. All you have to do is remove the plastic "gravel guard" (couple of bolts) under the front in order to get to it. My 00 V70 clutch was a little different so I found a $2 "For Sale" sign at Wal-Mart that was about the right thickness so that I could cut a custom shaped shim out of it.

You don't have to be a mechanic and even if you are not a "do it yourselfer" this will save you $$$$ and give a great deal of satisfaction. Even if it doesn't fix it, your only out a piece of cheap (or free) plastic and 20 minutes of your time.

Oh, you should use ramps so you can get ender the (edge) of the car. If you don't own any, borrow some or even buy some, the money you'll save will more than justify the expense.

Good luck!

You have the classic case of worn clutch which causes too wide of a gap for the clutch to pull in when it gets hot. It works OK until it drops out the first time. Measure the gap. If it's 0.030"-0.040" it's too wide and must be reduced either by installing the plastic shims (easy) or by removing shims from the clutch shaft (difficult).
--
Tom 69-1800S, 72-1800ES, 96-850T,2000-S70 GLT-SE

Are you saying that the compressor is NOT turning when the problem occurs, that is the first thing to know for any kind of diagnosis. If no then it is matter of checking for voltage at the compressor clutch and working backwards to the the relay, the low pressure cut out, then to the ECU. There are multiple diagnostic steps.
It is difficult if not impossible for the mechanic to diagnose without the condition occuring. Are you able to check for voltage and do basic tests? Otherwise the mechanic is just guessing and you don't want that.
--
David Hunter

There are many reports on the site of the compressor clutch wearing out to have too big a gap. I have this problem on my 95 850. When it occurs I can see the clutch trying to pull in but failing to go all the way. It snaps in if allowed to cool for a few minutes, or if carefully helped with a piece of wood or similar prod. The a/c will run for hours on the highway where air flow cools the clutch but it becomes balky in heavy traffic when things under the hood heat up lots.

A relationship to the alternator is unlikely. There is no system which takes loads away from the electrical system in case the alternator is weak or not working - except that when the starter motor is running the other loads are removed (so all battery power will be available to the starter).

A couple of things. Check the gap at the compressor clutch and look at this link: http://volvospeed.com/vs_forum/index.php?showtopic=80181

The compressor has a thermostat and if too hot will cut out. Don't ask me where it is, I can't make heads or tails out of all of the pictures :)

Klaus
--
I still miss my 164