AC compressor help

[HTX86chevy]

86 swb 5.7 ..... the compressor recently started acting up. it still blows ice cold and works fine while driving but vibrates excessively at idle! could it be the clutch or is the compressor shot? this only happens when ac is on loud excessive vibrating dissappears when i switch it off

[staggerd86c-10]

sometimes it might be that your a/c needs some freeon if its clicking on and off.

[jay55jay]

Maybe throw a extra can of oil charge in it maybe its Dry. Is the belt tight sometimes if its not to tight but tight it wount squeal but bounce just for thought.

[foamypirate]

I would check for any A/C lines that might be touching something they shouldn't. It's possible they could be vibrating at idle and causing the noise.

[James McClure]

It is an all to common practice to "top off" the system causing high head pressures and this of course leads to noise. Also is "harmonics" within the system. All things vibrateand they have a "harmonic threshold" where everything gets into sync and can cause some weird noises. Look for something loose\touching. If you topped it off, bleed it down. If all else fails and pressures are within spec, replace compressor and make sure you get the right ammount of oil in the system. jim

[HTX86chevy]

ok, i was watching this thing very closely the other day and yes the belt is doing the vibrating. pretty bad. it seems pretty tight though but as soon as i swicth the compressor on it starts vibrating up and down like a rubber band. it goes away when i accelerate though and it comes back later on when at idle..... any ideas???? loosen the belt or tighten it up???? maybe replace clutch???

[James McClure]

HTX, reading your latest info eliminates a need to replace compressor & the clutch isn't the issue either. It could still be overcharged. The belt, like everything else on planet earth, has a harmonic threshold. When stresses reach a certain point, these harmonics kick in and can be very destructive. The answer can be as simple as belt replacement or installing an extra pully\idler in the center of the offending belt section or doing some repositioning of components so you can use a shorter belt. Don't loosen the belt, it will slip and tightening it to much will hurt the water pump bearing. Make sure all components and brackets are tight and not cracked. Please keep us informed on your progress and what ultimately fixes this. It is a fairly common issue and others may need thie info. Jim

[Kalashnikov46]

^^^ agreed, i also know that when some of the a/c compressors would cause the vibration, sometimes it was simply fixed with a counter weight.

[Slonaker]

The compressor that you and I have (R4, I think...) is known for vibrating and making a moaning sound at idle. Mine has always done it.

Somewhere I have a copy of a bulletin from Chevy with instructions for fixing the moan, but it was considered optional if the customer wanted to pay to have it done. I think it required changing out the clutch, but I'm not sure.

Slonaker

EDIT: I have attached a copy of the three bulletins I have on the topic in PDF format.

[HTX86chevy]

OK, I MADE A QUICK VIDEO OF THE PROBLEM, SO THAT YOU GUYS CAN HAVE A BETTER UNDERSTANDING OF WHAT IS GOING ON BECAUSE I CAN'T SEEM TO FIND AN ANSWER. THE A/C BLOWS COLD. CLUTCH IS NOT STOPPING & STARTING, AND I DONT HEAR ANY CLICKS OR GRINDING.....

HERE IS THE LINK TO THE VIDEO:

http://www.youtube.com/watch?v=oFL81TrkUAw

CHECK IT OUT AND LET ME KNOW WHAT YOU THINK.

THANKS GUYS.

[3r!c84]

mine has the same problem only when in drive at a stop light with the ac on

[73chevyman]

i think your belt is bad i'd change that first but your clutch could be going.... that also could be the sign that it's low on freion

[HTX86chevy]

3r!c84, mine does exactly what yours does...... Does yours make a loud vibrating noise. I mean really loud!!!??????

73CHEVYMAN, DO YOU KNOW WHAT THE GAUGES SHOULD READ ON HIGH AND LOW SIDES???? I CAN CHECK IT OUT TOMORROW.

[James McClure]

HTX, a picture is worth 1000 words. What I say about the belt above? Your at the end of the adjustment, almost. Is the P\S belt the same way (almost at end of slot)? See if you can't get some belts that are 1 inch shorter or if that's not an option you can find, see if you can get wider. Those look like 7/16", go to 1/2". It won't take much to change the harmonic, let's just hope we change it in the right direction and move it up high enough so it's out of your normal operational band. Jim

[73chevyman]

i can find out for ya thats just a different subject i have not gotten in too yet lol

[73chevyman]

i was doing some extra reading on this and this could help you alot all you need to is lube your system and change the belts heres the article
http://townhall.edmunds.com/direct/view/.f0ead1f/78

[3r!c84]

Originally Posted by HTX86chevy

3r!c84, mine does exactly what yours does...... Does yours make a loud vibrating noise. I mean really loud!!!??????.

no it just vibrates the truck alot.. but when i get on the gas alittle and bring up the rpms to like 800(idle in drive with ac on is like 500) it stops vibrating.

i think its the thortel thing that pushes the throttel some when the ac is on to bring up the rpms isnt working..
sorry idk the name of the little guy

[blargh22]

I am having the exact same issue in my '88 suburban. I tried to tighten the belt but the issue still remains. I do suspect its a belt issue, as once hot it does seem to not be as tight. The AC is not blowing very cold, and I put 80% of 5.25 lbs of R134A in it, with about 8-9 oz of oil. It is blowing cold, about 60 degrees on a 100 degree day, but that does not really cut it in this weather. Is that normal for an R4, or should I be getting closer to 40 degrees?
The evaporator does get cold but doesn't feel ice cold to me. I was wondering if you ever got the issue resolved with the belt or not? I was planning on replacing the compressor. The compressor makes a lot of noise when in gear, but is quieter at idle. The belt vibrates a hell of a lot though, and the performance of the air conditioning isn't very good.

[Desert1957]

normal R4 operation , tighten all compressor mounting bolts

[Katrina/10]

Adjust your idle speed up or down till the noise goes away.

[blargh22]

Is there any reason to run R-12 in there over R-134A? Will that help the performance at all? I've been debating converting it back.

[anubisani]

Originally Posted by james mcclure

htx, a picture is worth 1000 words. What i say about the belt above? Your at the end of the adjustment, almost. Is the p\s belt the same way (almost at end of slot)? See if you can't get some belts that are 1 inch shorter or if that's not an option you can find, see if you can get wider. Those look like 7/16", go to 1/2". It won't take much to change the harmonic, let's just hope we change it in the right direction and move it up high enough so it's out of your normal operational band. Jim

i think u r right

[HTX86chevy]

Just an update for those who may be interested.
I found a "backyard" mechanic recommended by a family member.
This mechanic removed the Compressor, and showed me that it was full of black sludge.
he replaced the Compressor, orifice, drier and even installed an electric fan. he removed all the "ducts' and insulated/sealed up all the leaks under the dash. He also replaced the A/C lines with new ones. all the parts Came from a Local Parts Store.
I dropped it off before the weather heated up so that It would be ready for summer.
outside temps were cool so of course the interior temp was cold and I was happy. Paid him his $850 and rode off content.
Fast fwd a couple months, and now the damn thing is blowing 80 out the center vent with outside temps at about 98.
I took it back and he said he would fix it. He calls me two weeks later and says that he evacuated the system, removed & replaced the orifice, refilled everything to spec, wrapped the A/c box with insulation and changed the Fan clutch. Told me it was ready.
I cranked the truck up and noticed within 15 mins that it didn't change temps inside. still blowing 80 at center vent. I didn't pay him a dime more.... I took it to a Local shop with a good reputation and they said the Previous mechanic installed the wrong Orifice tube and never swapped out the condenser which is showing signs of restrictions due to the Readings on the Gauges and some Vacuum test they tried out to determine where the restriction was located! Should be ready tomorrow!!!!
WOW!
I'll update with pics and a short video.
Sorry for the RANT.

[hatzie]

The black sludge is called "Black Death" after the Teflon ring failures in the Ford FX15 compressors. You aren't seeing chunks of the compressor. The black crud you see is usually from overheating the compressor oil or contaminants leftover from not properly flushing the system or both.

Whatever the cause once the system is contaminated it's very difficult to get rid of it.