Need some basic A/C help... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-01-2008, 08:53 PM   #1
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Default Need some basic A/C help...

OK, California'* short, mild winter is over and it was 70 yesterday, which means the car heated up to 90 or so in the sun.

However, my A/C was blowing ambient temp air. I tried a recharge thingy from the parts puppies, and had A/C again for about 4 hours.

It'* apparent there'* a leak. Can someone tell me how to locate the leak, where it'* likely to be, if I have to evacuate the whole system and recharge, etc.?

I try to do all my own work without visiting a stealership, so be as specific as possible.

Thanks!
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Old 03-01-2008, 09:17 PM   #2
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I do my own AC, too. Leaks can be pretty hard to find. I hope you have (or have access to) a vacuum pump. Some approaches I have used: First, look for oily dirt around the joints in the system; that often indicates a leak. Oil on the compressor clutch is a giveaway, too. You can try, when the system is charged, to use a thin detergent and water in a spray bottle, and spray all the joints, including the compressor shaft end seal, seams and fittings, watching for the bubbles to grow where there might be a leak. If you have a vacuum pump, you can evacuate the system and pressurize it with compressed air for leak detection with the soap solution. I have found a long pump-down of a couple of hours works better than replacing the accumulator and pumping for 30 min the way many shops do. I bought a leak detector last summer from harbor freight on sale for $50 (?) I was unable to find any leaks with it. Not saying it'* no good, just my old cheapo methods had worked pretty well. For evaporator leaks, you almost have to have a detector, though.
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Old 03-01-2008, 11:43 PM   #3
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No luck with the harbor freight detector here either. Dad had a shop put dye in the system of his Town&Country, and when we pulled out the evaporator to replace it, all the dye was there & visible.
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Old 03-02-2008, 12:26 AM   #4
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Quote:
Originally Posted by John Deere Boy
No luck with the harbor freight detector here either. Dad had a shop put dye in the system of his Town&Country, and when we pulled out the evaporator to replace it, all the dye was there & visible.
Hmmm, maybe we'll have to spend more than $50. Thanks for mentioning the dye. I had good luck with the dye last year that clearly showed leaking o-rings in a compressor. Just bought it at WalMart for a few bucks.
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Old 03-02-2008, 02:21 PM   #5
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Hi,
Like Bill Buttermore said a 50/50 mixture of dish soap works good as a bubble leak detector. However I wouldn't recommend using compressed air to pressurise your system unless you have a great compressor that has a dryer on it. Reason being; compressed air has moisture in it and moisture kills a/c systems. Another reason being is the fact that your car uses HFC-134A therefore the oil in your system is an ester oil and ester oils are hydroscopic meaning that they are naturally drawn to moisture. If you introduce too much moisture to your system, chances are that even with a 29.9 inch evacuation you still wont boil all of the moisture out of your oil. Ester oils tend to become milky white and lose viscosity when introduced to moisture. Result; you would have to dismantle your system and change all oil. Furthermore if you jumper out your low pressure cut-out on your system and find that you have a low side leak, when your charge becomes low enough you will have a lowside(suction side) operating in a vacuum and you will be pulling noncondensables into your system. The best thing to do is to look for oil at fittings and use soap water mixture to bubble leak test these fittings.
The only proper way to pressurise a system for leak detection is to have your system'* refrigerant revovered. Then pressurizing the system with dry nitrogen, and "trace" amounts of refrigerent. After the leak is found the nitrogen can be vented to the atmosphere. Once the leak is repaired the system can be properly evacuated and charged accordingly.
Even if you find a leak the only way to fix said leak would be to have your system'* refrigerant recovered in order for to repair the leak. If you chose to vent your refrigerant to the atmosphere, under the clean air act (section VI) the EPA can assess fines " Up to $ 27,500 per incident, per day." and if someone reports you for doing so, they may recieve up to a $ 10,000 reward.
One more thing, when you add your cans of HFC-134A I assume that you are doing this off of the low side with the system running and the can upsidedown this is bad, unless you are charging into you accumulator, you are introducing refrigerent as a liquid into your compressor. Compressors cannot compress a liquid and doing this often will lead to premature compressor failure. Make sure that you hold the can upright so it charges as a vapor.
Also in my opinion, and alot of the people that I have worked with in the HVAC industry, dyes are not a good idea. They have not been proven to be harmful to a system but I wouldnt want to introduce another substance into my a/c system.
Just my $.02
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Old 03-02-2008, 02:50 PM   #6
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hvac guy: I charged my system with a can connected to the lowside with the compressor running, but i kept the can right side up so that liquid wouldn't be sucked in. It took a long time and i had to put the can in a bucket of hot water, but why do you say this isn't possible?
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Old 03-02-2008, 02:59 PM   #7
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John deer boy. Were you using a store bought can or a dot 39 cylinder? Anyway what I meant is that it isnt possible to charge off of the high side. sorry for the confusion, you did it the proper way.
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Old 03-02-2008, 03:02 PM   #8
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It was actually a can (small can) of Johnsen'* Freeze 12. From what i've read, it may eventually ruin my compressor, but I plan on replacing the compressor when i do a 134-a conversion anyway.
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Old 03-02-2008, 03:06 PM   #9
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When you do the 134A retrofit, make sure that you get as much oil out as possible as the CFC 12 uses a mineral oil and it is not compatible with HFC 134A.
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Old 03-02-2008, 03:14 PM   #10
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Quote:
Originally Posted by hvacguy
Hi,
Like Bill Buttermore said a 50/50 mixture of dish soap works good as a bubble leak detector. However I wouldn't recommend using compressed air to pressurise your system unless you have a great compressor that has a dryer on it. Reason being; compressed air has moisture in it and moisture kills a/c systems. Another reason being is the fact that your car uses HFC-134A therefore the oil in your system is an ester oil and ester oils are hydroscopic meaning that they are naturally drawn to moisture. If you introduce too much moisture to your system, chances are that even with a 29.9 inch evacuation you still wont boil all of the moisture out of your oil. Ester oils tend to become milky white and lose viscosity when introduced to moisture. Result; you would have to dismantle your system and change all oil. Furthermore if you jumper out your low pressure cut-out on your system and find that you have a low side leak, when your charge becomes low enough you will have a lowside(suction side) operating in a vacuum and you will be pulling noncondensables into your system. The best thing to do is to look for oil at fittings and use soap water mixture to bubble leak test these fittings.
The only proper way to pressurise a system for leak detection is to have your system'* refrigerant revovered. Then pressurizing the system with dry nitrogen, and "trace" amounts of refrigerent. After the leak is found the nitrogen can be vented to the atmosphere. Once the leak is repaired the system can be properly evacuated and charged accordingly.
Even if you find a leak the only way to fix said leak would be to have your system'* refrigerant recovered in order for to repair the leak. If you chose to vent your refrigerant to the atmosphere, under the clean air act (section VI) the EPA can assess fines " Up to $ 27,500 per incident, per day." and if someone reports you for doing so, they may recieve up to a $ 10,000 reward.
One more thing, when you add your cans of HFC-134A I assume that you are doing this off of the low side with the system running and the can upsidedown (since this is the only possible way that you could be doing it). This is bad, unless you are charging into you accumulator, you are introducing refrigerent as a liquid into your compressor. Compressors cannot compress a liquid and doing this often will lead to premature compressor failure.
Also in my opinion, and alot of the people that I have worked with in the HVAC industry, dyes are not a good idea. They have not been proven to be harmful to a system but I wouldnt want to introduce another substance into my a/c system.
Just my $.02
Thanks for the explanations. I used a 134a can with a gauge on top to fill into my low pressure side on a 98 last summer. I kept the can upright to let the freon vapor go into the system--not the liquid. I'm not clear about what you mean about holding the can upside down.

And thanks for commenting about dyes and other in the system. A neighbor loaned me a partly used can with gauge that he'd used from IC with a sealer and superrefrigerant in it. I used the gauge but didn't want to use much of the can because of the "extras" in the 134a. Do you agree? I went to the store and got my own with 134a only in the can.
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