Last summer I had the A/C recharged in my 1995 850 T-5R. According to the mechanic, there was absolutely no refrigerant left in the system. I had not used the A/C since the first year I owned the car (back in 2002), due to what seemed like a slow evaporator leak. But last summer I finally decided to charge the A/C, and it worked fine for the 2 months or so we used it.

This summer the A/C has slowly been crapping out on me, my guess being that the dreaded evaporator is at fault. The compressor has been clicking on and off at an increasing frequency, from once every 7-10 seconds to once ever 2 seconds.

Now for the funny part: The A/C continues to click on and off even when the A/C is set to the OFF position. The REC (Recirculate Air) button is also set to OFF, if it matters. And this issue seems to occur only when the car is traveling at a highway speed (45-50 mph or greater). When I drive on local roads, the issue does not seem as prevalent, as I've only noticed it on occasion.

As a result of this constant A/C cycling, I believe that my serpentine belt and pulleys are prematurely wearing out. I do feel a slight surge when the A/C kicks in, and I can't imagine this being a good thing for the engine and belts if done on a continual basis. I am now getting a whirring/groaning/screeching sound from the belt/engine area, which you can see a video of here if you're interested: http://www.youtube.com/watch?v=-9MvAjVXb7s

But I digress... so does anyone know why the A/C would constantly cycle on and off even when set to OFF? During past summers, when the A/C was completely out of refrigerant, I never experienced this A/C cycling issue when driving on the highway (or local roads, for that matter).

Any advice would be very much appreciated. Donations for my next trip to either Bankruptcy Court or a Cardiologist are also welcome. And I thought I swore off high-maintenance blondes a long time ago... guess not.

All the Best,

~MrPlow

Get a can of R134a and add it to the AC system. The port is directly behind the passenger side headlight with a black plastic cap that has 6Mn written on it. 6Mn means finger tighten only. You must have the AC switched on at that time.
The AC compressor turns on when the pressure exceeds 45psi and turns off when it gets below 23psi. R134a expands greatly when subjected to heat so the pressure is higher when hot. If the gas pressure gets too low, the compressor will not kick in except at engine start up/ check out.

There is no reason for you to ever shut off outside air by turning recirculate off. The ECC will do that for you automatically if the cabin temps get too hot. You should also never turn off the AC, let the thermostat do that for you. Just set it a 72F or 74F with the fan in AUTO, and forget about it.

On really hot or cold days, close the outside air vent in the center dash.

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)

Thanks for the fast reply, Klaus. If I were to just forego using the A/C indefinitely, would it be better to just let the refrigerant "run its course" and resume leaking out until empty? Or should I do some kind of manual flush of the system? I'd just prefer to deal with a non-functioning A/C than the constant slow leak/recharge process. I've dealt with having no A/C in previous summers, as it doesn't get unbearably hot up here.

It takes me 5 minutes to add a can of r134a and get the AC working again. My ECC is set to 74F in the summer and 78F in the winter, with the controls set to AUTO and the fan speed at auto. I never touch that part of the dash unless I need to defrost the inside of my window, which in Minnesota, I never need to do.

If you let the system get complete empty of r134a, the compressor will die.

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)