Any A/C experts out there?

Rogue Leader · May 1, 2012

So after incessant whining by the girlfriend after last race when we didn't have any A/C in the truck, and the impending 6 hour tow up to Loudon this friday, I decided to tackle the A/C tonight.

It started with the compressor not turning on at all. All fuses are good. I have a gauge, but obviously never showed anything because the compressor wouldn't cycle. Put a small can of 134 on it and after a few minutes the compressor started to cycle on and off. After about 15 minutes with the can on it it seemed to stop taking any more refrigerant, and putting the gauge on when the compressor cycled it said it was slightly overfilled. However the compressor was still just cycling on and off every 10 seconds or so. Now the ambient temp at the time was around 50 degrees so maybe that had an affect as well. The air that comes out feels cold-ish, but I know it won't be really cold since the compressor won't stay running.

Any ideas? What should my next step be? More refrigerant?

music · May 1, 2012

Did you have R134a in there to begin with?

Rogue Leader · May 1, 2012

Did you have R134a in there to begin with?

Yeah the condensor on the firewall says R134a on it.

00Silverado4x4 · May 1, 2012

No insult but when you were adding refrigerant were you also putting the oil in as well? I know you can buy cans with just the refrigerant but if your system is running low on oil your compressor will eventually fail due to no lube. Also are you running the AC on max when checking the pressure? Your readings will be off if not running the system at max.

Rogue Leader · May 1, 2012

No insult but when you were adding refrigerant were you also putting the oil in as well? I know you can buy cans with just the refrigerant but if your system is running low on oil your compressor will eventually fail due to no lube. Also are you running the AC on max when checking the pressure? Your readings will be off if not running the system at max.

AC was on Max and I believe the refrigerant was the one with oil, but TBH I would have to check. How many cans should it need to take if empty? Just one?

00Silverado4x4 · May 1, 2012

I don't remember right off hand how many, but I do know it will take more than one. When I moved to Georgia a few years ago I noted my AC was "cool" but not real cold. It took almost one full can just to get it from just in the "OK" region to "FULL" on my gauge. If I were to take a guess it'll take two or three to fill it up. Also if your AC has been non functional for awhile your filter drier may need replacing. Not sure how you can verify or how to replace it. I don't mess with the AC units in vehicles...the units I work on in the military are much bigger and real pain to work on...

Kind of looks like this...

http://www.groundequipmentsupplies.co.uk/pdf/05023.pdf

Rogue Leader · May 1, 2012

I don't remember right off hand how many, but I do know it will take more than one. When I moved to Georgia a few years ago I noted my AC was "cool" but not real cold. It took almost one full can just to get it from just in the "OK" region to "FULL" on my gauge. If I were to take a guess it'll take two or three to fill it up. Also if your AC has been non functional for awhile your filter drier may need replacing. Not sure how you can verify or how to replace it. I don't mess with the AC units in vehicles...the units I work on in the military are much bigger and real pain to work on...

Kind of looks like this...

http://www.groundequ...k/pdf/05023.pdf

I would assume its been non-functional for a long while (over 1 year) I got the truck in October, but it had been sitting for a good 5 months at that point. I'll have to pick up a couple more cans with some oil, and maybe check out the manual on what else it is, it didn't really have much on diagnosing compressor issues, but instead on just replacing it. Don't need that expense right now, plus if its just a leak, replacing it likely won't do a thing.

I have had 2 other GM vehicles in the past that behaved exactly the same and running a few cans through usually cured them, but its been about 8 years or so since the last time I did that and figured maybe it could be something else before I dropped 30 bucks on 2 more cans of stuff.

Doug_Scott · May 1, 2012

With R12, the a/c system would have a sticker on it saying how much refrigerant it held by weight. If the system was empty, there is a leak, and, the receiver/dryer would require replacement due to exposure to outside air. I stopped working on a/c just before the switch to 134a.

With R12 there was no reliable way to tell how much was in the system. R12 would be at 50psi if the ambient air temp was 50 degrees, and the compressor not running. With compressor running, high side pressure should be double ambient air temp. Low side should run at about 30psi and will cycle on and off.

waumo1 · May 1, 2012

One source I found says 32 oz, 36 oz for crew cab. One 12 oz can is not going to do it.

$15 for a 12 oz can? I'm glad I bought a 30 lb can when it was cheap!

Rogue Leader · May 3, 2012

One source I found says 32 oz, 36 oz for crew cab. One 12 oz can is not going to do it.

$15 for a 12 oz can? I'm glad I bought a 30 lb can when it was cheap!

$15 was a cheap one! Most were $20. Whats strange is though it didn't even take the whole can in, but it is behaving like it is low on refrigerant. There is still stuff left in the can, although maybe its not much.

Doug_Scott · May 3, 2012

One source I found says 32 oz, 36 oz for crew cab. One 12 oz can is not going to do it.

$15 for a 12 oz can? I'm glad I bought a 30 lb can when it was cheap!

$15 was a cheap one! Most were $20. Whats strange is though it didn't even take the whole can in, but it is behaving like it is low on refrigerant. There is still stuff left in the can, although maybe its not much.

Are you filling via high side or low side? If high side it will be difficult to get the can empty.

waumo1 · May 3, 2012

You really need a set of gauges to know what is going on but if it won't pull in even one 12 oz can no need to waste more time and $.

Did it really quit charging at less than one can, did the can get cold and you didn't warm it up or maybe you just didn't wait long enough for the can to completely empty?

Another problem you might have is if the system was completely empty and air/moisture got in the system, it might be freezing up.

00Silverado4x4 · May 4, 2012

Update? Curious minds want to know...

REVYCHEVY55 · May 6, 2012

Best bet get new accumulator / dryer, orfice tube and set of a/c o-rings (regular o-rings won't work) refrigerant oil for your model vehicle Break all joints and look at orfice tube for aluminum shavings. This is sign of compressor malfunction. Replace all o-rings coated with refrigerant oil including orfice tube. O - rin

gs at compressor may have to be bought sep

arately make sure they are the same thickness. GM has different ones for different models. Pour most of the oil in dryer the rest down suction side of compressor parts house should tell you which oil and how much to use. Make all joints back up and rent

REVYCHEVY55 · May 6, 2012

Sorry hit send. Vacum pump. This will remove moisture out of system. According to size of pump how long to evacuate system. Plus outside temp. But I would pull vacum as long as possible Less moisture colder air. Also it takes 15% less134 than R.12. Overfill with 134 and no cold air. You can find out how much 134 to use at parts house. Accumalator/dryer are not expensive here in miss 25.00 to 35.00 and they keep air cold by removing moisture. GOOD LUCK ! 96 degrees here today your gonna need good air this year