I just put a new compressor and dryer in my 01 tahoe. While adding freon the head pressure kept spiking above 350 so i would stop and wait for a few minutes. I got all the freon in but the ac doesnt blow any lower than 65 deg. The rear is colder than the front and when i stop at a light it starts blowing warmer air until i start to drive again. I took the blend door actuator off to make sure the actuator wasnt holding the door open. Same results. A friend said i have moistture in the system. Said i didnt pull vaccume long enough and that those autozone pumps didnt pull vaccume. This one pulled. -25lbs. The compressor is a new murray from orileys. Trying to figure out if the compressor is bad and if i just need to spend the extra money on a denso or a ac delco. Any help please.
AC issue
- Thread starter Brian7743
- Start date
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@UmmScott might have some guidance on this one.
You didnt pressure test nor evacuate the system properly.
-25inches Hg is not acceptable. You have a leak somewhere. Find and fix it. Put nitrogen in there up to 125psi and watch the gauges. If they drop more than 2 psi in 5 mins, you for sure have a leak.
After evacuating with a vacuum pump for no less than 30 mins, you have to reach 29.99inHG on the gauge.
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-25inches Hg is not acceptable. You have a leak somewhere. Find and fix it. Put nitrogen in there up to 125psi and watch the gauges. If they drop more than 2 psi in 5 mins, you for sure have a leak.
After evacuating with a vacuum pump for no less than 30 mins, you have to reach 29.99inHG on the gauge.
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Check your gauges and ALL connections. Make sure theyre tight.
Vacuum pump needs clear fresh oil in it.
If theres a leak, look around all piping and connections, especially the condenser. If u see any dark areas or areas where dirt/debris are clinging to the area, you've found a potential leak especially if its all oily at that area.
You're getting high head pressure because you pulled air into the system during your vacuum. 300psi is normal on a 100+ degree day but certainly not a normal day
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Vacuum pump needs clear fresh oil in it.
If theres a leak, look around all piping and connections, especially the condenser. If u see any dark areas or areas where dirt/debris are clinging to the area, you've found a potential leak especially if its all oily at that area.
You're getting high head pressure because you pulled air into the system during your vacuum. 300psi is normal on a 100+ degree day but certainly not a normal day
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Whats the full story on this? Has your AC been giving you problems: had to add refrigerant, never cold enough, never worked right?
Or.. did it work fine and suddenly the compressor failed?
All this info is good to know to help you out.
Last bit of info. You have to weigh in the amount that the system holds listed on the hood decal. Do not guess, needs to be weighed in. Not 4 oz more or 4 oz less but the exact weight
Let me know what more you find man [emoji106][emoji106]
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Or.. did it work fine and suddenly the compressor failed?
All this info is good to know to help you out.
Last bit of info. You have to weigh in the amount that the system holds listed on the hood decal. Do not guess, needs to be weighed in. Not 4 oz more or 4 oz less but the exact weight
Let me know what more you find man [emoji106][emoji106]
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Scott, yes my old system failed. I bought a new compressor and accumulator from autozone. I used one of their pumps to pull a vaccum for 20 min. Closed everything up and checked gauges.-25. Checked them again after 15 min and the gauges did not move so i didnt figure there was a leak. So then i started adding the freon. I had already put the oil in the pump before i installed it.
Ok cool
If you're 100% positive that there are no leaks and it will pull AND hold a vacuum, make sure you get the full charge in there..
Next. Report back with your running pressures both low and high side with the rear system on full speed max cold and the front system on full speed max cold and recirculation on. Let it run for 5 mins and see what your pressures are.
If you have high high side pressure again, like over 300 or 325, feel the liquid line feeding the front orifice. Its right where your gauges tap on generally. Is it cool or is it hot?
If its hot, then you're not removing heat from your condenser.
Remember... when compressors fail they can and will send particles downstream. This will clog up passages in the condenser coil giving you high head pressure that wont go away no matter how much air you move over it.
Sooo.... if you have high head pressure again, check, double check, and triple check your radiator clutch fan or electric fans whichever you have and make sure they're working correctly.
If... your condenser is clean on the outside of debris, your radiator is clean, your radiator fans are working good, and you still have high head pressure issues, then your condenser coil is internally restricted and you gotta replace it.
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If you're 100% positive that there are no leaks and it will pull AND hold a vacuum, make sure you get the full charge in there..
Next. Report back with your running pressures both low and high side with the rear system on full speed max cold and the front system on full speed max cold and recirculation on. Let it run for 5 mins and see what your pressures are.
If you have high high side pressure again, like over 300 or 325, feel the liquid line feeding the front orifice. Its right where your gauges tap on generally. Is it cool or is it hot?
If its hot, then you're not removing heat from your condenser.
Remember... when compressors fail they can and will send particles downstream. This will clog up passages in the condenser coil giving you high head pressure that wont go away no matter how much air you move over it.
Sooo.... if you have high head pressure again, check, double check, and triple check your radiator clutch fan or electric fans whichever you have and make sure they're working correctly.
If... your condenser is clean on the outside of debris, your radiator is clean, your radiator fans are working good, and you still have high head pressure issues, then your condenser coil is internally restricted and you gotta replace it.
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Should i just go buy another condenser? I also got a new orfice and the old one was perfectly clean but i replaced it anyway.
Yes the old compressor locked up.
Today i evacuated the system amd started over with a different vaccume pump. It sucked down to -30 pretty fast. I let it suck for 45 min. Shut everything off and waited 30 min and nothing changed.. No leaks. I added my freon and the results were the same. My low side is at 70 and high side 275. Still omly blowing 60 degreese. I have come to the conclusion that i am going to take this murray compressor back and spend the money on a denso. My clutch fan is working fine so i am going to get a condeser
Today i evacuated the system amd started over with a different vaccume pump. It sucked down to -30 pretty fast. I let it suck for 45 min. Shut everything off and waited 30 min and nothing changed.. No leaks. I added my freon and the results were the same. My low side is at 70 and high side 275. Still omly blowing 60 degreese. I have come to the conclusion that i am going to take this murray compressor back and spend the money on a denso. My clutch fan is working fine so i am going to get a condeser
Where are you located? What was the outdoor temps when u tested this?
Did u shut off the rear blower and set the front blower to the slowest speed?
Did you feel the suction lines coming back? Especially the accumulator for the front system?
70 is way too high on the low side unless its hotter than blazes outside AND inside the truck.
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Another thing, please double check on the parts you received especially the orifice and compressor.
Make sure they are for this vehicle and are for front AND rear AC systems.
Some parts guys are idiots/or just dont know this and dont ask or put that in the criteria. A single front system AC compressor will bolt right up to this truck and you'll have major issues.
Wouldnt hurt to confirm everything. Confirm what they sold you, what the box labels are and what the actual sticker on the compressor says.
Something is a miss here. But remember low side pressure and high side pressure are directly related.
Do this for me and yourself, take a garden hose and just drench your AC condenser with water while its running.
Pressures come down = either airflow issue or condenser is bad internally/plugged and needs replaced.
Pressures stay up = if they stay up but the piping leaving the condenser has cooled down, you've got air or noncondensables in there.
Try that. Easy test [emoji106][emoji106]
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Make sure they are for this vehicle and are for front AND rear AC systems.
Some parts guys are idiots/or just dont know this and dont ask or put that in the criteria. A single front system AC compressor will bolt right up to this truck and you'll have major issues.
Wouldnt hurt to confirm everything. Confirm what they sold you, what the box labels are and what the actual sticker on the compressor says.
Something is a miss here. But remember low side pressure and high side pressure are directly related.
Do this for me and yourself, take a garden hose and just drench your AC condenser with water while its running.
Pressures come down = either airflow issue or condenser is bad internally/plugged and needs replaced.
Pressures stay up = if they stay up but the piping leaving the condenser has cooled down, you've got air or noncondensables in there.
Try that. Easy test [emoji106][emoji106]
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I an in dallas and it was in the higher 80's. I did feel the line at the lowside abd it was cold at the lowside schrader valve but the closer i got to the highside schrader valve it got hot. I did not shut off the rear and turn the front on low. Didnt do anything with the rear accumulator. If there is one, i didnt know. I havent taken anything back there apart.
If the small line is hot to very hot on a day like 80F outside, then you're not removing heat from the condenser like you're supposed to..
Fan clutch, recheck it. Condenser is plugged internally and probably needs replaced
Dont return your compressor, sounds like its fine [emoji106][emoji106]
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Fan clutch, recheck it. Condenser is plugged internally and probably needs replaced
Dont return your compressor, sounds like its fine [emoji106][emoji106]
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Well i returned the murray and got the oem denso compressor i also got the new condenser and all is well now. Its blowing right at 45 deg in 85 deg weather. The condenser was the problem. Im sure if it. Thanks for your help scott. I have a much clearer vision on how it all works now.
