Non Cobra AC Compressor Question

ronzara · #1 (**permalink**) 06-01-2004, 09:31 AM

Hey Guys,

This question is on a 1995 GMC G2500 Vandura (5.7L). I just bought this Van to trailer my Cobra.
The Air Condition is NOT working. I was told it just needed charging. The compressor is making a very slight rattling sound, but it seems to be kick on when you turn the AC switch off and on.

So,... I recharged the system, but nothing...... (Still Blowing Warm).

I checked the front orphis (Van has front and rear air)... and it was COVERED in little metal particles.... the screen was about 90% blocked. I used a shop vac on the tube hoping to extract any other material that might be in there and installed a new one.
Replaced the O-ring and recharged,... Still blowing WARM.

The pressure gauge was showing about 90psi. (Pretty High)

I let it sit for about 8 hours.

Then Last night (when all was quit around here) and I could hear a HISSING coming from the Compressor.

After further investigation, I found that the Compressor was leaking on the rear around some sensor fitting. When I wiggled the sensor fitting back and forth, the leak got better then worse.

Apparently, there is a snap ring that holds this sensor recepticle in place, obviously with a failed gasket or o-ring.

I have never dug into an AC system. But I thought maybe one of you guys may have an idea about what these symptoms might indicate. ???? Any Suggestions?? (other than buy a FORD Van)

thanks!
RZ

Brewbaker · #2 (**permalink**) 06-02-2004, 06:37 PM

Hello Ronzara,

Here's more or less what you need to know about AC systems. 1. The condensor or evaporator are glorified radiators. They don't have moving parts.
2. The orifice is, well, an orifice.
3. The compressor has all of the moving parts. If you have metal shavings in your system, you must be generating it there.
4. The clutch mechanism is working if it is engaged while the AC is on and the system is charged with freon. Just make sure that the entire pulley is spinning on the compressor when it is on. If it is not engegaing, you will see the outside of the pulley spinning and the inside of the pulley will be stationary.
5. The accumulator is a sump. Often it has a desicant (spelling?)in it. If your system is exposed to atmosphere for a long time, you need to replace it. Typically, you are stuck replacing the accumulator with it as it is impossible to remove (on GM units at least).

So to troubleshoot, verify that the clutch is engaged. If not, find out why. Could be due to the leaking sensor. If it is working fine, then you most likely have a bad compressor. The low pressure side should be about half of what it is currently. The metal shavings are indicative of a moving part grinding, so again, this points to the compressor. If you replace the compressor, plan on replacing the dessicant with it. Before doing that though, try blowing out the system from the high side compressor outlet with compressed air. You might actually get some of the shavings out.

Good luck.

ronzara · #3 (**permalink**) 06-02-2004, 08:40 PM

Brewbaker,
Thanks for your insight. Most helpful. I should be recieving a new compressor in a couple days. I'll post my findings. Thanks again.
RZ

Ken Greene · #4 (**permalink**) 06-03-2004, 05:46 AM

dumb question but.... you are using a vacuum pump to evactuate all the system before charging right??? (only needed after changing parts of if there was a leak in the system that is now repaired)

ronzara · #5 (**permalink**) 06-03-2004, 08:42 AM

Ken,
No, we didn't use a vacuum pump. We did use a manifold gauge set, although, maybe we should've used the vacuum to remove all air before we started charging. We figured the oil and freon would push the air out of the high side fitting by cracking the gauge valve until we had liquid coming out of the line.....

You have shed NEW light on this thanks.
RZ

Ken Greene · #6 (**permalink**) 06-03-2004, 11:46 AM

two things can happen if you don't evacuate all the air in your system before charging
2 residual moisture will cause an early failure of parts due to not enough lubrication and.
2 the system not getting cold enough becuse of not the right amount of freon.

i dont know alot about small things but i know a little about a lot of things

ronzara · #7 (**permalink**) 06-10-2004, 09:26 AM

OK,

We now have COLD air! Found the compressor WAS bad and also the rear air Expansion valve. I replaced both parts and a new orfice tube, blew out the lines, then used the vacuum pump as recommended. Everything is working properly and blowing 58 degrees in our Myrtle Beach humid 90 degrees. Total cost was around $200 (and this is including wasting 2 charges worth of oil/refrigerant trying to diagnose the problem). A repair shop would've gotten me for about $600 or more!
You came through once again.

Thanks for all the help guys!

RZ