Air Conditioning ?
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
Air Conditioning ?
I’ve searched the site but have been unable to find the info I’m looking for so here’s the scoop. I know it’s not a corvette but it is a Chevy we will be talking about. 
When I bought my 1992 K2500 Suburban 7 years ago the PO told me it needed an A/C Compressor. I didn’t care because it was going to be a plow truck until now I need to drive it in the heat. 110 heat index today.
The compressor only kicks in if I jump the harness for the pressure switch so it does in gage the clutch. Even with the switch jumped it still blows hot air.
It has already been converted to R134a so I bought Freon and tried to re-charge the system but it didn’t take much? And did not change anything still hot air.
What could a possible cause be? Is the compressor actually bad? Any help Appreciated.
When I bought my 1992 K2500 Suburban 7 years ago the PO told me it needed an A/C Compressor. I didn’t care because it was going to be a plow truck until now I need to drive it in the heat. 110 heat index today.
The compressor only kicks in if I jump the harness for the pressure switch so it does in gage the clutch. Even with the switch jumped it still blows hot air.
It has already been converted to R134a so I bought Freon and tried to re-charge the system but it didn’t take much? And did not change anything still hot air.
What could a possible cause be? Is the compressor actually bad? Any help Appreciated.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
I’ve searched the site but have been unable to find the info I’m looking for so here’s the scoop. I know it’s not a corvette but it is a Chevy we will be talking about.
When I bought my 1992 K2500 Suburban 7 years ago the PO told me it needed an A/C Compressor. I didn’t care because it was going to be a plow truck until now I need to drive it in the heat. 110 heat index today.
The compressor only kicks in if I jump the harness for the pressure switch so it does in gage the clutch. Even with the switch jumped it still blows hot air.
It has already been converted to R134a so I bought Freon and tried to re-charge the system but it didn’t take much? And did not change anything still hot air.
What could a possible cause be? Is the compressor actually bad? Any help Appreciated.
When I bought my 1992 K2500 Suburban 7 years ago the PO told me it needed an A/C Compressor. I didn’t care because it was going to be a plow truck until now I need to drive it in the heat. 110 heat index today.
The compressor only kicks in if I jump the harness for the pressure switch so it does in gage the clutch. Even with the switch jumped it still blows hot air.
It has already been converted to R134a so I bought Freon and tried to re-charge the system but it didn’t take much? And did not change anything still hot air.
What could a possible cause be? Is the compressor actually bad? Any help Appreciated.
Get some gauges and see whats in there. You can jump the low pressure switch for a FEW seconds in order to get a compressor to generate low pressure to suck in some gas. BUT, if you have too much and the low side climbs to near the high side, somethings gonna blow apart. 134a is very delicate when it comes to the quanity. Its only 90% of what r-12 was used in that system. It needs a different expansion valve, a clean condensor and a good dryer and the right oil.
Get some gauges before you get hurt. Those lines can come apart before you can blink...
I can tell you now that if you had to jump the low safety switch, its probably got no gas, but it should take gas if the compressor is turning at fast idle. You have to have gauges to see if the comp is actually creating pressure on one side and low pressure on the other.
Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
I dont know a lot about a/c stuff but try using a vacuum pump on the system before you add any freon. Then fill to proper pressure using gauges to be sure. At that point the compressor should kick on by itself. If it doesnt more diagnosis is necessary and that is beyond my skill set.
Drifting
Joined: Nov 2008
Posts: 1,307
Likes: 25
From: NY NY
I would pull a vacuum for well over an hour on that system sounds like you have some sort of a vapor lock possibly some moisture in there. Recharging, the compressor will come on when the right pressure is reached and fill to recommended charge.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
those things basically act as super fine filter and yes they do get build up and/or clog over time. The orifice tube will be close to the evaporator. It shouldn't be too hard to find look for a fitting(s) in the middle of a hard line about 5 or 10" away from the evaporator housing. If you "open" the system to change the oriface tube at a minimum you'll want to change the accumulator as well.....vacuum the air/moisture out of the system before recharging.Change the compressor, accumulator(dryer) and the oriface tube at the same time....they may sell a 'kit" that contains everything you need(oil, gaskets, flush(optional), etc) Make sure you tell the parts guy/gal this is a R12 to 134A swap out as the parts may vary....oils, pressure switches, oriface tube, etc.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Another option is to go to an A/C shop and have them do an evaluation. Many times it is free and you can see and ask questions as to what is going on. You may need some expertise to get you over the knowledge hump to get you problem resolved. If the shop can fix it easy, then the next time you will be more ready with additional information.
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Le Mans Master
Joined: Jul 2005
Posts: 5,193
Likes: 16
0 on the high side...never seen that.sounds like it wasn't hooked up right, check the gauge hose for a fitting which depresses the shrader valve on the condenser port..sometimes they are missing..you should have something in the high side even if the compressor doesn't run.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
I agree probably something wrong with the high side hose/hose fitting/service port fitting/gauge there. When an AC system has been shut "off" for extended periods of time and if the system has any type of charge at all the pressure should be pretty much = for both the high and low sides (which is normal).....until the compressor actually runs/turns "on" the then the high side should go up.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
The orifice tube's purpose is to allow the compressed liquid to expand into a gas. That is where the system gets cold. They have no filtering ability. It is a small opening and subject to clogging if small particles get into the system.
Thread Starter
Pro
Joined: Nov 2009
Posts: 583
Likes: 0
From: Maple Grove Minnesota
Gage test was done both static and running with the pressure switch jumped to in gage the compressor.
Blend door is functioning as it should.
Is the orifice tube on the high side? if it is it could be clogged not allowing refrigerant to the compressor?
Blend door is functioning as it should.
Is the orifice tube on the high side? if it is it could be clogged not allowing refrigerant to the compressor?
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
No incorrect - there is a filter built into the body of oriface tube - the filter is before the small piston hole. This filter keeps particles from clogging the piston hole. The piston is the hole where the freon state is changed.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
This is done without ever opening any valves on you manifold gauges, keep them closed at all times.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
Hey - your back - this is not even relevant to the thread though so I'm not even why your making an issue of it. It is near impossible to clog one of these....even with AC system leak sealer.
No incorrect - there is a filter built into the body of oriface tube - the filter is before the small piston hole. This filter keeps particles from clogging the piston hole. The piston is the hole where the freon state is changed.
No incorrect - there is a filter built into the body of oriface tube - the filter is before the small piston hole. This filter keeps particles from clogging the piston hole. The piston is the hole where the freon state is changed.
Last edited by MK 82; Jul 26, 2011 at 12:21 AM.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
Not trying to make an issue at all. I think you and I both understand the system. However your statement gave the impression that the purpose of an orifice tube is to act as a filter. The tube may or may not have a screen to trap particles prior to the orifice itself. Sorry if I upset you.
