I guess this is round three of my questions on my 1999 V70 T5's air conditioning system. I replaced the condenser last fall after we hit a deer. There were some other issues before, but here's the current problem:

System holds charge just fine. When the car is first started, the ac works great. For 5 minutes. Then it shuts off. It is not a compressor clutch issue. The compressor comes on and stays on for the full 5 minutes, then it shuts off and won't come back on. No cycling. Just full-tilt compressing followed by nothing. I'm guessing the compressor overheats? The rather rudimentary low-pressure-side gauge that I have says the charge is at the right level while the compressor is running. Once it stops, though, the pressure goes quite a bit higher--into the red zone. When the car is off, the pressure is at the right point.

Have I just overcharged the system? Is this a sensor issue? Where to begin?

Thanks . . . AC has never been my specialty.

Nate

Is radiator cooling fan clicking on when it should?

Did you cut the wires to the thermal switch yet?

The compressor only cycles when the cabin temp gets close to the proper temp setting, or the R134a gets low. And, yes, the pressure should go into the red when the compressor turns off - the gas expands a lot when warmed up.

Make sure the bread clips are still in place, and check the clutch gap with a feeler gauge. The gap must be less than .040 and ideally around .020.

Klaus
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My name is Klaus and I am a V ♂ lv ♂ holic

Thanks, Klaus, for the reply! Can I just cut the thermal switch wires, or should I just jumper around it? I will do that today and see what happens.

I'll dig in further today. Thanks so much!

Nate

The thermal switch consists of 2 wires going into the opposite side of the compressor that the clutch is on. From Volvospeed:
bypass the a/c thermal switch. Took me a while to find it, and even when i did find it, i was nervous about cutting it, afraid i was going to break something... but i said what the hell, my a/c is already broken anyway, lol.

it was kind of tough for my big hands to get to it, but i was able to snip the wires that go into the side of the compressor on the opposite side of the clutch (drivers side of the compressor, included a picture before i snipped it), and i fed the wires to the top (the wires were really really short), then took a wire nut, and tied the two together.

just by doing that, i was able to bring my a/c from working randomly, to working nearly 95% of the time.

Now, its probably a good idea to do the clutch gap fix. i havnt gotten to that yet, but i believe that is also a problem on mine (and most 850's). because my a/c still kicks out at times and blows out warm again, but only under hard acceleration (>4500rpm, or kick down initiated... sometimes it will knock it out, sometimes it wont.).

So basically, the thermal switch bypass worked wonders for me. now i can sit comfortably in stop-and-go traffic without worrying about the a/c.... it blows out ICY COLD even in the 90+ degree heat.

(picture shows the compressor from the underside of the car, which is the easiest way to get to the thermal sensor. Its the little brass-looking piece with 2 wires coming out of it)

The picture is from the under side of the car, very fuzzy, but shows the two wires going into the back of the compressor. "I" would cut the wires with just enough length left to crimp them back together again, just in case??? I like the plastic wire nut to join the two wires heading back to the car, it is much easier to join them that way.


The whole VS topic is here:
http://volvospeed.com/vs_forum/topic/76833-ac-thermal-switch/

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My name is Klaus and I am a V ♂ lv ♂ holic

Well, I jumpered the thermal switch (which, on mine, happened to be on the side of the compressor facing the headlights). Now the ac blows ice cold and doesn't turn off! I guess my bread clips are still working.

Thanks again for the hints . . . I feel like I'm finally starting to understand the air conditioning system. At least somewhat.

Nate