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  • 1 Post By springhillracer
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  #1  
Old 07-06-2011, 04:21 PM
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AC Help PLEASE

alright, so Im going to burn my excursion...A couple weeks ago, I noticed the a/c in my truck at times would blow warm air. One day I was in the truck and I heard a noise and my ac started blowing warm, the noise stopped and it was cold again. I run an auto shop, brought my truck in and the a/c clutch was slipping. Ok, it has 111k on it, time for a new compressor. I swapped the compressor, orfice tube and accumulator. The orfice was clean as can be. I vac the system for 45 minutes, charge 4.25 pnds and my high and low side were through the roof. 350-400 and 70-80 on the low side. Figured I got a bad compressor, it happens. Warrantied the parts, flushed the condenser, which was clean. No medal in system. Evac and recharges again....same thing. Same pressures. My fan clutch seems to be working ok, but just to be safe I installed a aftermarket fan onto the condenser. This did not help AT ALL. Still high pressures. Do I have another bad compressor? I have done plenty of a/c jobs and this is driving me nuts. I know with the added ac in the rear and just over 4pnds my pressures are gonna be high, but not this damn high. My suburban has rear ac also and at 4pnds of freon its around 275-300 and 50....WHAT NEXT? Do I have a weak fan clutch? I was going to mist the condenser and see if this helped at all. Any thoughts?
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  #2  
Old 07-07-2011, 06:16 PM
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Your compresser is fine and doing a good job I might add. Do you have anyway to raise the idle speed ( 1200 RPM ) so you get more air flow when testing? ( Good time to do the hi-idle mod) Still sounds like you have air in the system with pressures that far out of wack. Are you recharging with 134A? Your pressures sound right for R22.

What is your sub cooling value on the liquid line?
What is the Super heat value on the suction line right after the evaporater ?
Temp outside?
Temp inside?
Saturated Condensing temp?
Saturated Evap temp ?
Suction line temp?
Liquid line temp?
temp drop across the evap?
What did you use for a vac pump?
What level of vac did you get to before you recharged?
Are there bugs and or a trash bag stuck to the condensor?
We can help you solve this if you can provide more data please?


Looking at the pressures you provided your evaporator is about 72 deg and you are condensing at 175 deg if you are using 134A. If the inside of the truck is 100 deg your evap temp is pretty close to being correct. So on the outside it looks like you have air in the system, your condensor fins are beat to He!!, Your mesuremnts are at 600 RPM idle and you arn't getting much air flow ( ditch the Electric fan it's just a restriction ) OR you are not using R134A. MORE INFO PLEASE ???

Last edited by HAM_RADIO_MAN; 07-07-2011 at 06:31 PM.
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Old 07-08-2011, 04:12 AM
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My condensor fins are ok, the occassional bug and dirt, but not bad. I do believe I have a clogged condensor or an air flow problem. Being that I added a fan and it didnt help and my cooling fan is working as designed, I am going to replace the condensor. My orfice tube was clean. I used a Robinair a/c machine. Vac system to 27" for 45 minutes. I amd going to do it for an hour and a half once I get the condensor in. Yes Im charging with 134. I didnt measure any temps before or after evap or condensor. I will install condensor and go from there. Only other thing is a collapsed hose causing a blockage.
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Old 07-08-2011, 01:27 PM
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I am pretty sure your condenser is OK, since the problem started with a bad compressor clutch. When you pull a vacuum next time shut it off and see how long it holds a vacuum in the system. If you can’t hold a vacuum for at least 45 min you still have a leak. Right now I am thinking pinched o-ring at a connection or some other leak. 27 in of vacuum really isn’t that good a vacuum in an A/C or refrigeration system. You could have a leak that is pulling air in to the system almost as fast as your pump is pulling it out. Any excess air will accumulate in the high-pressure side and lead to very high pressures and decreased performance. This is because the air is taking up space in the condenser and even though you have 4 LBS of 134a in the system the orifice tube is still starving for liquid. I can tell you more if you can get the data I spoke of in the last post. If you head pressure is high and your sub cooling is low there is very likely air in the system. Good Luck.
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Old 07-08-2011, 04:39 PM
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i vac it again today for 90 minutes. Our machine reached 30" of vac and after the 90 minutes, it did a 10 minute leak test. According to the machine it passed. I could not get you accurate temps today because it rained all day. My pressures looked good because of the low temps outside and the ac was cool. I will let you know how it does when its 100 outside. As far as some of the data, Im not sure how to measure some of it. As far as the temp drop across the evap and cond I can do that. And also, I just thought of something, I think my old compressor was still good, it wasnt noisy, just kept slipping the clutch. Well, this compressor did that also, once, when the high side got to high. I am guessing that the old compressor just couldnt handle pumping that high of a pressure and a worn clutch (111k) couldnt hold tight against the hub, therefor the clutch "slip" occurred. I replaced the condenser because I did notice that if I driving, moving air through it, it was cooler. I thought either its the lack of air flow, or a clogged condenser. I know my fan is working, so I replaced the condenser. It was cheap and I had nothing else to do at the shop today...lol. After that i pulled it into a 90 minute vac. Like I said, I can measure some of those temps when the weather gets hotter... How can you test these fan clutches? How do you know if they are working like they should? I had our gauges hooked up today and I noticed the fan doesnt get going until the high side gets quite high? I monitored the fan with a scanner, it does free spin then also go into a faster spin, but its almost like its "lazy" and takes a very long time. Any way of testing? Sorry for the long post and thanks. One more thing, about a year ago, I noticed a kinda tinny ticking sound from dead center in the engine up front. Kinda a weird noise so I started to disassemble to find out what it was. I got down to the water pump pulley and noticed it was cracked, i thought for sure that was it. Noticed a sligggghhhhht play in the water pump, but I let that go and replaced the pulley. THought for sure that was it. NOPE. Still there. So i just drove it for a little while, thought maybe it was the WP. Replaced the pump a few months ago, Noise still there. Im assuming its the fan. All the pulleys are good. Sounds right in the middle of the engine near the fan. Could this be something?

Last edited by springhillracer; 07-08-2011 at 04:46 PM.
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Old 07-08-2011, 05:06 PM
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Sub cooling is the difference between the readings on the temp scale on your high pressure gauge and the measured temp of the liquid line at the pressure tap port. This tells you how far below it’s boiling point at that pressure the Freon is cooled. This tells you about condenser effectiveness, charge level and a few other things

Superheat is is the difference between the readings on the temp scale on your low pressure gauge and the measured temp of the suction line after the evaporator at the pressure test port. This tells you how far above it’s boiling point at that pressure the Freon is heated. This tells you about evaporator operation, charge level and if any liquid is getting to the compressor.

As to your noise. What about the bearings in the fan clutch. Bad fan clutches KILL water pumps everyday. I don’t know much about the electro-viscous fan clutches on these engines so those are questions better answered by someone else. Sorry I will have to keep my advise to you confined to topics that I know what I am talking about or else I am really no help to you. Keep us post and I’ll help ya with what I can.
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Old 07-08-2011, 05:07 PM
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It might very well be time for a new fan clutch. I am pretty sure your problem is AIR.

1. Fan clutch might be slipping or bad and thus no air flow for condensor

2. There maybe air in the high pressure side of the system.

As i think more about this issue, If I were to put more time and money into the problem I would look real hard at the fan clutch. So now it sort sounds like the fan clutch failed and caused the system pressures to spike putting extra load on the compressor. The compressor clutch started slipping and failed. Now the fan clutch is still a problem and you are fighting that problem before it kills the 3ed compressor. I am just trying to put all this together in a way that makes the facts fit a theory, just a logical guess.

Last edited by HAM_RADIO_MAN; 07-09-2011 at 03:35 PM.
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Old 07-08-2011, 06:36 PM
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Keeping track on this. Some good reading
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Old 07-18-2011, 07:44 PM
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Did you get it fixed yet?
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