I had the ac recharged at a shop and it worked great for a couple of weeks. Now, the compressor cycles about every 10 seconds at 87 degrees F and doesn't cool. I attached a small gauge that comes with a refill kit and the pressures are cycling between 45 and 25. From what I read, this is normal cycling pressures. I checked the heater coil and the shutoff is completely retracted, which I believe is closed. What should I check next?
Marlin

Edit: I also used air and water to clean the condenser and the fan comes on with the compressor.

The "short cycling" is a sign of low freon.
Most likely you have a slow leak.
Why was it recharged? Was a repair done.
Normal procedure to find a slow leak is to put in a leak detector with the freon.
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David Hunter

I was feeling brave last night so I added a partial can of 134A to the system. This boosted the low side pressure to about 45psi when the compressor was running. I used the same gauge to check the pressure on my wife's '93 940 and hers was reading 55#, so I felt comfortable with the pressure and the compressor stayed on. It's cooling now, so I'll keep an eye on it. Thanks for the help.
Marlin

Recharged for the same problem I'm having now, not cooling well. The shop told me that the control was bad because it wouldn't turn on and they had to "jump" it to get it charged. Control seems to be working, so I don't know if they know what they're talking about or not. No repairs done as far as I know. 4 or 5 years ago I had to replace one of the hoses to the compressor and the receiver/dryer.
Marlin

When freon is very low you do have to jumper the pressure sensor to get compressor going and proceed with charging, that is normal. As it leaks away again it will stop cooling and short cycle just as you described. Eventually it will get very low agian and stop the cycling
I would say again you have a leak. Did the shop check for leaks?
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David Hunter

I don't know if they checked for leaks when I had it recharged, but it sounds like I should take it in to have the pressures checked and ask them to do that if the pressure is low. I looked last night and all the connections look clean. I don't see any obvious areas of oil seepage. Thanks for the help.
Marlin

Many leaks will not show up as oil seepage: small leaks can only be detected by an R134 sniffer. By law, they are supposed to test for leaks and repair before refilling: you may be using a less than qualified shop. And ask them to refill using a dye leak detector for future ease of finding leaks.
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See the 700/900 FAQ at the drop-down menu above right.

This used to be the best shop in town and conveniently located within walking distance of work, but I'm becoming less confident of their work. In the past year the shop manager has tried to tell me how much more they know about my Volvos than I do (big mistake), failed to tighten the lug nuts on a co-worker's car, and told me that the control panel wasn't working on my ac (seemed to be working fine, just the "backwards" on/off button typical of a 940). I think I'll try another shop next time.
Marlin

I think rapid cycling is a sign of low refrigerant.

At last that's what THIS SITE says, in describing the 850 Clutch Cycling Orifice Tube system, which is the same as ours.

Try googling on CCOT rapid cycling for more opinions.
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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.