New AC Compressor Noise - LS1TECH

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New AC Compressor Noise

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Old 04-15-2012, 05:32 PM   #1
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Default New AC Compressor Noise

I wonder if you gents could help me with this...

My AC hadn't worked since I purchased the car several years ago. Having wanted it for a while, I finally decided to fix it. I replaced the compressor, accumulator, orifice tube, soft lines (suction and discharge lines), and all seals. I added 8 oz. of PAG 100 oil to the compressor as I installed it. I then flushed the evaporator, condenser, and the hard liquid line using a blow gun and AC flushing solvent from Advanced Auto. I then hooked up the vacuum pump and let it run for 1.5 hours, then waited a half hour to be sure it held the vacuum. I then added 24 oz. of r134a.

The first time the compressor engaged, it sounded perfectly normal. Later, after the engine had warmed up, when I engaged the compressor, it made a noise akin to an engine valve-train when the engine has no oil. The noise stops a few seconds after the compressor starts and then sounds normal. Today I investigated farther. Watching the gauge set as the car ran at idle, with the AC set to max, lowest fan speed, the low side was at 26-29, the high 200-225, all with an ambient temperature of 76 F. With it running as such, the vent temperature is 39 F. When the fan is set to high, the low side is 31-36 PSI and the high 200-250 PSI. When it reaches a tad over 250 PSI, the fan kicks on until it drops to 200. Vent temperature is about 45 F on this setting. With the fan speed on low, the compressor sounds normal. With the fan speed on high, when the high side reaches 250 PSI, the compressor starts making the noise. It will continue making the noise on this setting regardless of high side PSI. If I switch to the low setting, as the high side falls through 225 PSI, the noise stops. The low side will drop to 26-29 PSI. When the compressor is not making the noise, it sounds just like the compressor on my friends 2000 Alero (using an automotive stethoscope to compare).

I'm just trying to figure out if I did something wrong, the compressor is defective, or there's just some odd issue at hand. Thanks for any suggestions!
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Old 04-15-2012, 06:53 PM   #2
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how did you add 24 ounces of r134a?
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Old 04-15-2012, 07:30 PM   #3
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Where did you add the lubricant?

You did divide the oil up and add it to all the components, correct? Should be 2oz in compressor, 2 accumlator, 3 evaporator and 1 condensor. You should also turn the compressor about 10 times to lubricate it.

I just replaced all my ac stuff as well, but I had a bad compressor. It made a slight metal on metal noise out of the box when I would spin it, but thought it was because it didnt have any lube in it. I installed everything and the ac blew cold, 35 degrees, but the noise continued to get louder. I evacuated everything and found that the compressor had blew metal all through my system. So i warranty replaced it with another one.

Sorry for the long post but, I would take the belt off and spin it by hand to see if the noise is still there.

1998 Trans Am
ATK 408, s480, Huron Speed front mount, Tick Specd Cam, Jakes Stage 3 TH400, Moser 9", Tuned by RPM, 819 RWHP @ 12.5 PSI.
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Old 04-15-2012, 09:32 PM   #4
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Thanks for the replies. I used two 12 oz. cans of refrigerant from an autoparts store. They were the ones that had r134a only, no additives. I added ~3 oz to the compressor, ~3 to the accumulator, and the rest in the evaporator. I did spin the compressor 10-15 times to lube it and didn't feel any abnormalities or hear any odd noise. I'll spin it by hand again. I just don't understand why it only makes the noise under certain circumstances. If it was bad, I would expect it to always make it and for it to get worse as it ran. I sure hope it didn't blow metal through the system. Did you just flush yours? Should I replace the accumulator again if I find metal?
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Old 04-16-2012, 08:42 PM   #5
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first off with a new system i wouldnt have charged it with the cans from the autoparts store i would have used a robinair machine or took it somewhere to get charged with one to know ur getting the correct amount of refrigerant. Another thing is did u charge the high side with the car off or the low side with the car running?
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Old 04-17-2012, 10:38 AM   #6
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Try dropping the pressure. But, still it should not be making noise at 250 psi.

I seen compressors run to 325 without noise.

Possibly a bad compressor out of the box. It just can't handle running pressure.
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