Just curious if anyone knows at what point low the pressure switch dis-ables the compressor? Had my system converted 2 years ago and cooling was o.k. for 2 L.A. summers but this spring I noticed the compressor not kicking in. After searching archives here I learned how to jump the switch to check compressor. I then added one can of r134 and a leak sealer/oil charge tune-up deal. Hard to get a decent reading with one of those low side gauges but on a warm day the vent temp at idle gets to about 50 or 55. Yesterday it was in the 90's here and driving in stop and go the vent was between 60 and 70. A bit cooler today and the comp. was cycling a bit, vent temp on freeway between 50-55. This is a 240 so capacity (if it were R12) is 46 or 48 ounces, can't recall which. I have a feeling I'm still a bit on the low side but don't want to overcharge. I'd appreciate any advice on the matter.
Oh, I noticed also yesterday when I tapped on the expansion valve the vent temp dropped a couple of degrees.

As always, advice is greatly appreciated.

thanks
Kirk S.

I think the proper charge of R12 is 38oz. The expansion valve thing sounds suspect. Did you have it replaced with an R134a expansion valve at the time? If not you should consider doing that, if the valve seems to be sticking.

Although it could be frozen if the charge is that low. The low pressure cutoff is very low on the 1990 and earlier 240s. It isn't really a pressure cycling system like the later ones, so the low pressure cutoff is just a safety threshhold that insures the comp is still getting enough oil.

It could be in need of a charge, but the best way to do that would be to... recycle the refrigerant and charge from scratch. It needs to charge into a vacuum, though, so you wouldn't really want to take ALL of the charge out. Leave a little residual R134 in the system so it's still a little pressurized, then charge until vent temps are proper. Without pressure readings it's hard to tell what the problem is.


--
1992 940 wagon, 72k
make people envious; smile often.

thanks Chris,

I didn't have the expansion valve replaced when converted because I didn't know then what I know now about a.c. systems. Actually, I learned most of what I know from this board and aircondition.com over the last couple of months. I thought my a.c. dead until I started researching and figured I'd give charging a shot, which was successful to the extent that it's now blowing cold air at least, but I read many posts warning of overcharging r134 so I didn't want to make that mistake. This is Volvo #3 for me so I was trying to avoid taking it anywhere, maybe an investment in manifold gauges would be the way to go for me at this point.

By the way, I took your advice from the other day on my other 240 and had it converted to Freeze 12 yesterday (only 97.00) and that seems to be working fine.

thanks

Kirk S.

Wow, less than $100 for WORKING air conditioning. That is truly impressive.

Don't worry. At the cheap cost of 134, you are hardly out any money if you have to replace the valve and refill the system. It's not a big deal at all.
--
1992 940 wagon, 72k
make people envious; smile often.

Yeah, I was pretty impressed with the price of the Freeze 12 conversion myself. As far as the r134 system goes I think I'll charge with manifold gauges to proper charge and see how it goes, if I need to change expansion valve at some point I think I'll be confident enough by that point to tackle it. I have access to a pretty heavy duty air compressor, any idea how the cheap-o air vacuum pump would work in this situation?

thanks again,

Kirk S.