A/C noise?

[scrobbyd]

Okay so I just bought a brand new AC Delco a/c compressor and dryer. After flushing all a/c lines, condenser, evaporator core, replaced orifice tube I added 4oz of oil to the compressor and reassemble everything with new o-rings. I pulled a vacuum on the system for one hour then let sit for about two hours no loss of vacuum. I then took a can of a/c oil and put in the system first with my pressure switch my past and used about 3/4 of the 8 1/2 oz can. Next I added 3 12oz cans of R134 to the system. AC is blowing ice cold, no complaints where that is concerned! However I've developed a noise while the compressor is running. The best way that I can describe it, is it sounds like a heatshield rattling against the exhaust. Strangely it only does this at bout 1000 RPMs. Any ideas? Thanks in advance...


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[Chuck Leeper]

Too much oil?
Hi and lo pressures are? Freon added while watching the gauges?

 

[scrobbyd]

Yes I was watching gauges. Hi-Lo 30/45


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[BuickMike]

I'm assuming your compressor is the universal one that everyone sells? I think it's called the service unit. I'm also assuming that the noise is only just off idle. You can check to make sure that all the bolts that hold the AC bracket to the head are tight, but these units are known to have a vibration/ noise just off idle and it is annoying. I was very detail oriented when redoing my AC system and I have the same problem with that compressor. It's been working perfect for 2 years now with no issues other than that noise. I don't see it reported that much here, but found complaints on other G Body forums when I was trying to figure out what was wrong with mine. If you fix all the rattles / things touching under the hood, it will be less noticeable. It vibrates bad at that RPM and tends to make stuff such as a metal SLIC shroud make noise. I luckily kept my old OEM style one and will have it rebuilt by a local shop if this one ever dies.

 

[Nick Micale]

I have replaced over 100 AC compressors on TR's and quit using AC Delco a few years ago when they moved production to China.

One reason was the noise you mentioned on a few of them, and was not happy replacing them for free.

The 4 Season's brand has never had that issue on the one's I installed, and it has double the warranty of the Delco compressor.

 

[BuickMike]

Thanks for the added info Nick. When I first posted about my compressor noise awhile back, nobody here had any knowledge about this common issue and it sent me down a long rabbit hole that included me RMA'ing my first one for a replacement that did the exact same thing. It wasn't until I searched on the compressor in general that I saw plenty of others with different vehicles having the same issue. For now my remedy is to turn the stereo up louder.

 

[scrobbyd]

Thank you for the responses! Okay so my plan is to return this new AC Delco since I can because I purchased on Amazon, luckily!!! I will find the 4 seasons compressor since Mr Nick has had success with them and opt out of BuickMikes radio theory (LOL) sorry Mike. I think the only question I have left here now is for Mr Nick. Should I flush everything again, replace orifice & dryer or dump 4oz of oil in new compressor pull vac then recharge? Thanks for the help guys! Mr Nick if you have a part # handy on that 4 seasons compressor it would be great if not no biggie I'll figure it out. Thanks again



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[Chuck Leeper]

Yes I was watching gauges. Hi-Lo 30/45


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Those pressures are way off. {assuming you are running the engine at elevated rpm, fan on]
Low side should be 10-20, and hi side ambient + 100.
We just finished a new charge of 134 on another car. We saw the above pressures.
Your pressures are far too close together. [Pressure differential].
If the system is working well, those numbers are bogus....

 

[BuickMike]

Good point Chuck. Those pressures are not right, however if he has ice cold air, the pressures he posted are not what he really has. If he was really seeing those pressures, the orifice tube would be bad and the air would be warm. All that being said, I thought the low pressure switch will turn off the compressor if it senses anything below 25 or 30psi? I don't remember exactly what it is set to, but I remember it being a bit on the high side for R-134A. I've had to charge mine to keep a good 30+psi on the low side, which sucks because the high side pressure is higher too and thus generates more heat. My car runs warmer with R-134A than it did with R12.

 

[Chuck Leeper]

Good point Chuck. Those pressures are not right, however if he has ice cold air, the pressures he posted are not what he really has. If he was really seeing those pressures, the orifice tube would be bad and the air would be warm. All that being said, I thought the low pressure switch will turn off the compressor if it senses anything below 25 or 30psi? I don't remember exactly what it is set to, but I remember it being a bit on the high side for R-134A. I've had to charge mine to keep a good 30+psi on the low side, which sucks because the high side pressure is higher too and thus generates more heat. My car runs warmer with R-134A than it did with R12.

Maybe, look at 15-20 on the low side. Adjust the low sw to just below that?? I last saw that the sw should be set to 21... Not sure if that'll work.

 

[scrobbyd]

This is the pressure chart I used in coordinates with 90 degree outside temp.

Then adjusted my pressure switch to 30/45. 30 being the lowest I could get for it to cycle. Just by what I've read the ideal cycle was 20 to 25.




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[Chuck Leeper]

Good point Chuck. Those pressures are not right, however if he has ice cold air, the pressures he posted are not what he really has

Looks like the psi posted is the low side. }Hi-Lo 30/45}.There was no hi listed. That's what I was wondering about.

 

[Wahoo]

I do hvac for a living. 134a Temp/pressure chart pressure of 30psi =35 degrees, 35psi= 40degees, so anywhere from 30psi to 40 psi with engine around 1,500rpm would be good to me. But if at idle it still should be at least 30psi.

The compressor is not supposed to be short cycling on the low pressure switch, it should only turn off when you turn it off. The low pressure switch is a safety switch for when you lose refrigerant so it doesnt run in a vacuum or empty.

 

[scrobbyd]

I do hvac for a living. 134a Temp/pressure chart pressure of 30psi =35 degrees, 35psi= 40degees, so anywhere from 30psi to 40 psi with engine around 1,500rpm would be good to me. But if at idle it still should be at least 30psi.

The compressor is not supposed to be short cycling on the low pressure switch, it should only turn off when you turn it off. The low pressure switch is a safety switch for when you lose refrigerant so it doesnt run in a vacuum or empty.

So wahoo are you saying my numbers look good? If not then what is my corrective action? Is so what is causing the noise? Thanks for the input you guys

 

[Chuck Leeper]

If not then what is my corrective action? Is so what is causing the noise?

I think a compressor change is in order, considering what Nick described as his discovery ofthe cause....

 

[Wahoo]

So wahoo are you saying my numbers look good? If not then what is my corrective action? Is so what is causing the noise? Thanks for the input you guys

You have to check the pressures at idle and at 1500-2000rpm with fan on highest speed, setting cooling on max.

If theyre in between what i said and the temp coming out is in the 40s charge is good.

But if the noise is still there, could be a mechanical problem with the compressor like they said above.