a/c compressor not engaging

'95 Caprice wagon.

When we first got the car running I noticed that the a/c wasn't working. Didn't think much of it since the car sat for 14 years, just figured the freon leaked out over time. When we had the car at the shop getting the new tires installed we had them vacuum down the system and recharge it. He said the ac was working before they did anything. They still vacuumed the system, added dye and some oil and recharged it, I think it was less then 1/2 a pound low.

After getting the 'new' gas tank back in the car I went for a drive around the neighborhood today and the a/c wasn't blowing cold at all. Opened the hood and the compressor isn't engaged. The dash controls function properly.
What should I check out? Seems like it's an electrical issue?

After the shop charged the system, did you use it? The symptoms you have usually mean your AC is not charged.

Tom

silverfox103 wrote:

After the shop charged the system, did you use it?  The symptoms you have usually mean your AC is not charged.

Tom

Yes it worked fine when we picked the car up. The car has been sitting for a couple weeks since then. And the guy that did the work is a good friend and the shop foreman/master tech at the local Ford dealer.

Sounds like you have a slow leak. If you want to see if the compressor is working:

- start car
- turn on AC
- remove two prong connector on drier (low pressure switch)
- take a wire, insert into connector to complete circuit (loop between contacts)
- compressor starts, good, it works, remove wire
- find leak, fix, vacuum, add R134a to fill

So I jumped out the low pressure switch and the compressor kicked on...

I'll borrow the UV light and see if I can find a leak.

Is there a way to check/test the low pressure switch itself?

Check pressure before doing replacing switch. Pressure too low? Leak (unless your garage didn't fill all the way). Pressure correct? Change the switch.

You can get a good (and cheap) gauge set at Harbor Freight.

All the B-bodies I've worked on eventually leak either at the test ports or the compressor nose seal. Switch aside, given the age of these cars, I'd bet money you've got a leak at either of those places.

So this morning the a/c clutch went up in smoke! Wife came back in the house to tell me about it and show me a pic of the smoke coming from the compressor area under the hood! She switched cars and went on to work.
I just looked at it after I got home from work. I unplugged the clutch wiring and then started the car. The clutch wasn't engaged but it did sound like a box of rocks rolling down a hill! I guess the compressor gave up the ghost... Time to replace the a/c components! I suppose the car is gonna sit now until I can replace the parts. Hopefully within the next week...

Any suggestions on a compressor, lines, condenser and other related items? I see RockAuto has a bunch of compressor options. I will go with new over rebuilt.

anyone?

Just replace the compressor.

jayoldschool wrote:

Just replace the compressor.

Any opinions on a particular one?

The lines look to be in rough condition as well...

a couple mechanics I know prefer the four seasons brand components, but I would also check the orifice tube to see if there's debris in it, which is in the lower tube at the condenser.

I ended up getting a Delphi compressor and new lines. Changed out the parts today, took a good portion of the day to do.

There was nothing in the system...

When I pulled the old lines out there was a pretty significant rub/wear spot where the line runs past the control arm.

Did you protect the new line with a section of heater hose on the upper A arm?

jayoldschool wrote:

Did you protect the new line with a section of heater hose on the upper A arm?

not yet but I will. I couldn't find my scraps of hoses in the garage yesterday...

As a follow up, the Delphi compressor locked up shortly after install but before I could get the system charged! Not sure how or why the clutch engaged if there was nothing in the system and the low pressure switch should have kept the compressor from trying to run... The switch tested OK with my meter, showed as being open as it should have with no pressure on it.

I ended up getting a new AC Delco compressor (made in China), I also replaced the condenser (made in Taiwan) and the receiver/dryer. I added oil to the compressor and the dryer, about 2 ounces each, the compressor came dry. Brought the car over to a buddy's shop and we vacuumed and purged the system a couple of times, which sucked a couple ounces of oil out. We added a couple ounces of oil back in and filled with about 1.75 pounds of 134A. a/c blows good and cold! Had about 45-50 degrees from the vent with the car idling for a while. The car was running long enough that the electric fan cycled a couple of time, so now I know that also works. Of course the temp gauge never moved higher then the 1/3 of the way up position it always shows once warmed up.

Thank you for following up. When you first installed the new compressor, did you turn it over several revolutions by hand to pump the oil out of it before you started it? For the compressors that come full of oil, this is critical. Compressors do not do well pumping liquids, whether refrigerant or oil.

I did spin the first one by hand, actually blew the shipping cover off the ports and shot oil all over the work bench!

The second new one I added oil and turned it by hand a few times as well.