Automotive Air Conditioning Information Forum (Archives)

scottmcbee on Sun June 24, 2012 9:11 PM

Year: 2004
Make: GMC
Model: Sierra 3500
Engine Size: 6.0
Refrigerant Type: R134a
Ambient Temp: ~90
Pressure Low: 0
Pressure High: 0

I went to replace my comp and accumulator (and orrifice tube) for the third time now. All were operator errors except the first time, which I have no idea why my compressor locked up. Over the last few days I have replaced the compressor, accumulator, orrifice tube, and added a inline filter that was $50. I then bought a harbor freight vacuum pump and mani guages.

My question is this- I pulled a vacuum and it went down to 30 very quick and left it for an hour. It lost vacuum in 5 mins. I have 6 cans of r134a and a robin air leak detector. Should I pull vacuum and switch hoses as fast as I can to get r134 into the system so I can sniff out the leak, or, just put the r134 in without vacuum? I'm new to this but have read a lot on these forums. Any help is greatly appreciated.

buickwagon on Mon June 25, 2012 12:39 AM

Quote
Originally posted by: scottmcbee Should I pull vacuum and switch hoses as fast as I can to get r134 into the system so I can sniff out the leak, or, just put the r134 in without vacuum?

The purpose of drawing a vacuum is to get rid of any trace moisture or air. I personally thing attempting to draw a vacuum in a know-leaky system is just sucking more moist air into the system.

The approved method of finding the leak is to install a few ounces of R22 then pressurize with dry nitrogen.



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I've saved hundreds on service by spending thousands on tools.

scottmcbee on Mon June 25, 2012 12:51 PM

Well, like I said it vacuums to 30 and it stays at 30 until I turn the pump off. Then it drops steadily over 5 or 6 mins till its back at zero. So there's no way I can check the leak with r134 and a electronic leak detector? I don't have compressed nitrogen. Just compressed air, and its by no means dry.

scottmcbee on Mon June 25, 2012 12:56 PM

I've checked the pump and guages now, and its def not them. I hate that I just spent all this money on the vacuum and guages and am still having to go pay $100 plus to have it done.

mk378 on Mon June 25, 2012 3:29 PM

For a leak that large, start at zero psig (full of air), put in R-134a up to 10 or 20 psi, and start checking with electronic leak detector.

Edited: Mon June 25, 2012 at 5:52 PM by mk378

scottmcbee on Mon June 25, 2012 4:10 PM

I found it! The cycle switch on the accumulator had cracked down the treads. $20 and its holding good now. Knock on wood. I just hooked a can of r134 up and barely let any in and heard it hissing right away. I know that may be bad but I just let a little gas in. The switch is 4 inches away from the port. Hopefully it won't do any harm. Thanks guys for your replies. I have another project I'm starting next week so I may need some help then! Thanks again.

Dougflas on Mon June 25, 2012 4:25 PM

Quote
Originally posted by: buickwagon
Quote
Originally posted by: scottmcbee Should I pull vacuum and switch hoses as fast as I can to get r134 into the system so I can sniff out the leak, or, just put the r134 in without vacuum?



The purpose of drawing a vacuum is to get rid of any trace moisture or air. I personally thing attempting to draw a vacuum in a know-leaky system is just sucking more moist air into the system.



The approved method of finding the leak is to install a few ounces of R22 then pressurize with dry nitrogen.


This is incorrect. Do not ever add R22 into a mobile AC system even with N2 to find a leak. The R22 will permiate the rubber hoses. You will be chasing false leaks. Then later on, if you charge the system, the R22 can contaminate the R134.

scottmcbee on Mon June 25, 2012 5:09 PM

Yeah I knew better than that. I think he just said r22 meaning refrigerant.. But I know enough to not add anything other than r134a to a r134a system.

mk378 on Mon June 25, 2012 5:53 PM

I would also suggest that after 3 blown compressors, your condenser is going to be clogged up with metal debris.

scottmcbee on Mon June 25, 2012 6:04 PM

Yeah I think I still have a problem. I charged it and it went to 40psi with just 1.5 12oz cans of r134a. It blew cold. Now I think I made a big boo boo. I put a inline filter on the system. It said to put it on the low side. I just realized that its just before the high side port! I had the lines off the truck and on a 2004 GMC sierra 3500, the high side is just a few inches from the low side port, orrifice tube and expansion valve between them. When I charged it, the pressure on the high side was at 280 but now has dropped to about 225. I'm going to have to recover, and replace the line now right?

scottmcbee on Mon June 25, 2012 6:15 PM

I take that back. I got the instructions out for the inline filter, and it says to mount it before the orrifice tube. That just so happens to be just before the high side port. Did I mess this up?

Also, ambient temp is about 95 right now, so where should my readings be on high and low side.

I feel like there's a lot of pressure built up behind the quick coupler on the high side. Kinda scared to remove it.

scottmcbee on Mon June 25, 2012 6:35 PM

I'm an idiot . I was reading the inner ring on the guage, I should be reading the outer ring right? Wow. The outer ring (says r134a on it) says +6 low side, +58 high side. So I'm just now starting to get it charged, right?

I was supposed to have a HVAC buddy of mine over here that's done this a lot, but he couldn't make it till next week so I tackled this myself. Should have waited I guess.

mk378 on Mon June 25, 2012 6:55 PM

Read very outer scale, the one that is psi. When working on a stock system with a specified charge amount, always install that charge then evaluate performance.

buickwagon on Mon June 25, 2012 11:14 PM

Quote
Originally posted by: Dougflas

This is incorrect. Do not ever add R22 into a mobile AC system even with N2 to find a leak. The R22 will permiate the rubber hoses. You will be chasing false leaks. Then later on, if you charge the system, the R22 can contaminate the R134.

I did not mistake R-22 for any other refrigerant. I described the EPA approved method. According to the EPA:

R-22:
(a) creates a leak path because of its oil solubility and residue displacement potential;
(b) is more readily detectible by electronic leak detectors than HFCs;
(c) is non visual-dependent, unlike dyes, thus can be used effectively to locate leaks in enclosed areas;
(d) will not cross-contaminate nor cause any harmful consequences to CFC, HFC, nor blend refrigerant systems (i.e., after leak testing an HFC (R-134a) system using R-22, there is typically zero percent cross-contamination if evacuated afterwards).

Nitrogen summary. Nitrogen has the following qualities:
(a) inert, very dry and non-flammable;
(b) does not go into solution with refrigeration oil to create non condensable pressure problems (i.e., after leak testing an HFC (R-134a) system using R-22 and nitrogen, there is typically zero percent non condensables (nitrogen or air), if evacuated afterwards).

Under the EPA definitions, the R-22/nitrogen combination is NOT a refrigerant and can therefore be released to the atmosphere -- ie: it is legal to put it in a known leaking system. Installing R-134a into a leaking system is not allowed.

Hey, I don't make these rules, I'm just quoting them.

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I've saved hundreds on service by spending thousands on tools.

Dougflas on Tue June 26, 2012 7:33 AM

Quote
Originally posted by: buickwagon
Quote
Originally posted by: Dougflas


This is incorrect. Do not ever add R22 into a mobile AC system even with N2 to find a leak. The R22 will permiate the rubber hoses. You will be chasing false leaks. Then later on, if you charge the system, the R22 can contaminate the R134.



I did not mistake R-22 for any other refrigerant. I described the EPA approved method. According to the EPA:



R-22:

(a) creates a leak path because of its oil solubility and residue displacement potential;

(b) is more readily detectible by electronic leak detectors than HFCs;

(c) is non visual-dependent, unlike dyes, thus can be used effectively to locate leaks in enclosed areas;

(d) will not cross-contaminate nor cause any harmful consequences to CFC, HFC, nor blend refrigerant systems (i.e., after leak testing an HFC (R-134a) system using R-22, there is typically zero percent cross-contamination if evacuated afterwards).



Nitrogen summary. Nitrogen has the following qualities:

(a) inert, very dry and non-flammable;

(b) does not go into solution with refrigeration oil to create non condensable pressure problems (i.e., after leak testing an HFC (R-134a) system using R-22 and nitrogen, there is typically zero percent non condensables (nitrogen or air), if evacuated afterwards).



Under the EPA definitions, the R-22/nitrogen combination is NOT a refrigerant and can therefore be released to the atmosphere -- ie: it is legal to put it in a known leaking system. Installing R-134a into a leaking system is not allowed.



Hey, I don't make these rules, I'm just quoting them.

What you are quoting is for commercial and residential HVAC systems that do not use rubber type hoses that MVAC uses. R22 gets permiated into rubber MVAC hoses. A proper type leak detector will indicate a R134 leak. A 609 EPA license does not allow the licensee to purchase R22. Using a R22 with N2 in mvac will have you chasing your tail for leaks.

buickwagon on Tue June 26, 2012 8:29 PM

R22 won't penetrate barrier hoses.

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I've saved hundreds on service by spending thousands on tools.

TRB on Tue June 26, 2012 9:18 PM

R22 should never be introduced into a Automotive system. I've seen R22 destroy Barrier and non Barrier hose.

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