Aaron R.

Last year I put a new (not rebuilt) a/c compressor on my wife's 1987 IROC 5.7 TPI 700R4. I also replaced EVERY component of the a/c system (evaporator, drier, orifice tube, pressure switch, lines), except the condenser which was still good. The a/c blows nice and cold (about 45* at the vent with 95* outside) at highway speed. At low speeds in town or stopped in traffic the vent air doesn't blow as cold, but I assume that is probably normal given it is running R134 in a system originally designed for R12.

Here is the problem:
When stopped at idle the compressor makes a LOT of vibrations that can be heard and felt throughout the car. It's a loud growling noise that just sounds terrible. It is especially bad if the car is in gear (automatic). As soon as you speed the engine above idle the growling goes almost completely away and it isn't noticeable inside the car, but I can still hear it a little if I put my head under the hood. At idle the a/c v-belt also bounces up and down a lot. I have the correct new Gates belt on it and it is adjusted correctly. As soon as it goes above idle the belt smooths out and the growling goes away. I heard that low battery / alternator voltage sometimes causes the compressor voltage to drop too low, but I checked the battery with a voltmeter and it holds steady at about 14 volts when the compressor is engages on and off. I got tired of it and assumed it was a bad compressor even though it still cools fine and replaced the compressor with another brand new one this month. My 1985 Camaro Z28 needed a compressor so I put the other one on it. Her car still growls and is exactly the same. With the a/c working on my car I noticed it too growls and vibrates from the compressor, although it is not as noticeable since mine is a 5 speed standard and doesn't idle with a transmission loading the engine.

I don't know why else it would be doing this, other than both compressors are somehow not built correctly and I don't want to just throw compressors at it since they are about $200 each. I have heard a lot of bad about rebuilt compressors, and I can't seem to find any new units that aren't manufactured by 4 Seasons. I bought the first compressor at O'Reilly's a few years ago and it sat on my shelf until putting it in her car, and the other new one I bought last month at Autozone. Both were made by 4 Seasons and just branded with different part numbers.

OrangeBird

iTrader: (1)

https://www.thirdgen.org/forums/cool...e-systems.html

If the above link works , it'll take you to a thread that basically says our stock compressor is better to be swapped with the sanden unit . If it makes you feel any better , mine growls at idle too , goes away at any throttle above idle and cools the car well , and has been that way a good number of years now (it's growled ever since I've owned it) ...

Aaron R.

OrangeBird thanks for the link! I read it and a bunch of similar links and the Sanden swap looks like a great idea, and fairly easy. I think when I get ready to put the a/c system in my 1983 Chevy truck I will go the Sanden route. The compressor I have on her car came with a lifetime warranty and I don't feel like spending more money on a kit or fabricating brackets myself for a Sanden unit so I decided to experiment a little more to see if I could minimize the growling. If I can just reduce the growling and get the new compressors to last a few years I can live with it I think. R134 is really cheap at Wal-Mart so draining the system every few years only cost me about $15 total for 3 cans.

I had some old cans of EnviroSafe 12a sitting on my shelf and had decent performance out of it in a different 1987 Camaro years ago so I decided to try it. EnviroSafe is isobutene (basically propane WITHOUT the added sulfer, which is destructive to all the aluminum in an a/c system). The 12a specs say to NOT pull a vacuum on the system, so I drained the R134 and dumped about 1 can of it into the system. It worked, but wasn't charged nearly enough and cycled constantly at idle and so much at increased rpm that it was hardly cooling at all. I tried to put another can of 12a in, but for some reason the a/c system would not pull any more in at all. With nothing left to lose and running out of ideas I tried adding a can of R134. It pulled in about 3/4 of the can and the a/c system began to cool very well. I checked the low side pressure and found it running about 50psi. It was 70% humidity and 85*F outside. My chart says the low side pressure should be 45-55psi at that temperature, so I took the car out for a drive. It just about froze me out with 31* at the vents during highway speeds and about 43* at the vents while stopped. I had already realized the growling at idle seemed directly related to the amount of charge in the system (more charge, more growling), but with it at the correct pressures and charge level it was still growling so I increased the idle speed a little bit. That helped, and I also noticed that it growls noticeably worse when the car is first started and the longer you run the a/c the less it growls to the point it pretty much goes away. Just finished test driving it and am very happy with it right now, but I'll let the car sit for a bit and maybe check it again later or tomorrow.

ScarabChris

I had a similar issue on my 87 GTA. This is what I did...made my own extra pulley. Works like a charm. No more belt slop.

ScarabChris

Not sure if you will be able to view this video but this is the pulley running on my FB page.

Aaron R.

I like that. Looks very easy to make. Is that just a roller bearing with large washers on each end?

Did you have growling come the a/c compressor too and if so did this fix it?

ScarabChris

I got the pulley and shaft from Grainger and made the bracket from some steel stock. The pulley has roller or needle bearings and the shaft comes with a grease fitting so you can grease it without taking it apart.

It did help the growling but didn't eliminate it completely. These old style compressors are just loud. I have had a bunch of older GM cars with this compressor and they all did the same.

The extra pulley was more for the belt slop. With the AC on that belt would vibrate up and down a good inch. Now it has zero slop.

Aaron R.

I was digging through some of my old threads and realized I never posted an update to my fix for this problem.

Long story short it was caused by system pressures getting too high, discovered when I monitored the high side pressure gauge and noted it way too high. The high pressures were caused by too much heat accumulated in the condenser. I fixed all this by installing a Dakota Digital fan controller and wiring it to turn one engine fan on anytime the a/c is operating (a/c modes and defrost). This kept the condenser cooler, improved low speed interior cooling, and reduced the high side pressures and strain on the compressor that was causing all the vibrations and noise.

Vader

Better late than never. That's a great reminder to everyone to check overall system performance when affecting repairs and adjusting.

It may have been acceptable with the original R12 since that has a higher latent heat capacity than R134A, so the factory got by with not altering the fan scheme for a few years until dual fans came into play.