after car warms up compressor belt slips, bad compressor or something else?

Discussion in 'The Big Chill' started by torqueaddict, Jun 27, 2014.

  1. torqueaddict

    torqueaddict Well-Known Member

    Hi - I have a 72 Skylark, with a 71 455 that I put in last year. Engine seemed to be running great and I just got the a/c working in it.

    I noticed twice during a drive the smell of the belt slipping and a/c not working. Popped the hood and I see the belt slipping on the compressor pulley or the pulley barely turning. I have a new belt and it's nice and tight.

    I asked an A/C guy and he said try hosing off the condenser in front of the radiatror next time to see if the compressor start turning correctly again. I tried that today and it seemed to correct the problem. It was really hot.

    So does this mean the compressor is probably fine and I have some other engine cooling problem?

  2. Steve Craig

    Steve Craig Gold Level Contributor

    Pulley should be turning at all times with the engine running. Activate the electric clutch by turning on the AC & the compressor will rotate.
    Take the belt off & the pulley should turn freely by hand.
    I'm thinking you may have a front bearing gone on the compressor.
    Front bearing is an easy fix but you'll need a puller to get the pulley off.
    Myself & others here have done it with home-made pullers.
  3. torqueaddict

    torqueaddict Well-Known Member

    Do you still think it could be that even when belt slippage stops when I turn ac off?
  4. Steve Craig

    Steve Craig Gold Level Contributor

    Turning the AC on engages the electric clutch. Once engaged the belt & pulley are rotating the compressor itself. If this is when the slippage occurs, sounds like you have an problem internal to the compressor. Bearings are a common failure with cars of this vintage.
  5. torqueaddict

    torqueaddict Well-Known Member

    Still, I am thinking you may be right. I was trying some things with it today and I accidently put my hand on that compressor pulley and I pretty much burnt an impression of that pulley on my hand!

    Maybe a bad bearing and/or clutch can cause belt slippage only under load (compressor engaged)?
  6. Steve Craig

    Steve Craig Gold Level Contributor

    Sounds like the electric clutch is working as once engaged you see an applied load.
    The bearing can be changed with the compressor in the car.
    Going out right now but do a search on bearing change for AC compressors.
    Made a puller from hardware store parts.
  7. telriv

    telriv Well-Known Member

    Sounds to me like the compressor is low on refrigerant oil. Add 4ozs. to the system right away. System holds 10ozs. if an A-6 compressor. This should solve the problem short term. If it does you eventually need a compressor. Better to do it sooner than later BEFORE the compressor self-distructs & runs metal throughout the system. Same thing as what happens when you run an engine low on oil for awhile. Add oil & everything appears to be OK for NOW, but eventually you are looking at an overhaul.
    If this doesn't solve the problem no harm done.
  8. torqueaddict

    torqueaddict Well-Known Member

    Thanks great suggestion!

    I can just add it like I am adding refrigerant? It will take it even if the system is fully charged? Do you know what weight I need? (I think there's 3 types at autozone)

    Any chance a bad clutch could do this? I understand now the bearing is not the issue since it does not spin when clutch is engaged.
  9. telriv

    telriv Well-Known Member

    Would depend on the refrigerant you are using, 12 or 134. It will state it on the can. Can be added with system full, of course added to the low side with the engine running & the A/C on. A bad clutch will not cause this. Although since the clutch has gotten so HOT/OVERHEATED the grease in the bearing has melted to the point of being at the stage it will be N/G shortly anyway. When the clutch is not engaged the bearing is still spinning. It NEVER stops spinning as long as the belt is still in place. Also the facing of the clutch will be very worn, it can be refaced, since it was slipping for a period of time. When you take it apart you will notice little shims that set clutch clearance which you need to measure. Doesn't take long to destroy components when there is an overload in the system somewhere. I have removed the clutch & bearing with the compressor installed on the car. Easy on the Buick's of your years, plenty of room to accomplish this. No need to remove any freon as the seal is on the shaft. Removed the bearing & the grease seals on the bearing very carefully to not destroy the seals, cleaned it out, checked for roughness & wear & have repacked the bearing with Kendahl Super Blue wheel bearing grease with a good success rate. Although a new bearing is cheap enough, but being the cheapo that i am, I am willing to put in some time to see if something/idea will work, on my own time of course, to try & save some $$$ down the road. This of course depends on the integrity of the bearing to begin with. Like I said, "if the oil added remedies the problem you are going to need a compressor soon anyway". Better to replace now than later. The old saying is soo true, "Pay me now or pay me more later", your choice.
    Searching around there is not much of a $$$ diff. between new & rebuilt. I would ALWAYS go new if available & try to stay away from "foreign" replacements.
    Again, just my thoughts on the subject.

    Tom T.

    Tom T.
  10. torqueaddict

    torqueaddict Well-Known Member

    thanks for all the info!

    I added the oil, but still getting the belt slippage. While I was adding oil i noticed that when the belt was slipping the pressure was really high-off the chart. But then if the compressor started turning again, the pressure would return to normal.

    Is this typical behavior? I think I may be ready to have a pro look at it again.
  11. telriv

    telriv Well-Known Member

    Too much freon????
  12. torqueaddict

    torqueaddict Well-Known Member

    I ended up taking the car back to the a/c place, and they replaced my compressor. Drove the car a few hours over the weekend while running the ac so that was it.

    Interestingly the compressor it aluminum so maybe it's one of the modern replacements.
  13. TexasJohn55

    TexasJohn55 Well-Known Member

    You have already identified the problem and it was high head pressure, (off the charts). If you are running the original condensor with r134a it was likely overcharged. The system will not live with pressures over 350 psi for very long. I have seen new compressors blow from high head pressure.
    You need to leave the guages on it and drive it in hot weather to monitor pressures, tie the guages up at windshield if necessary to watch them. Insufficient air flow from broken shroud or a weak fan clutch can cause problems at low speed. Even under optimum conditions, without an upgraded condensor for 134a you will have high pressure. The compressor was not the cause, just the victim.
  14. gregg1

    gregg1 New Member

    I agree with TxJohn55 to some extent. You said that applying water to condenser made compressor start working again, this indicates poor air flow across the condensor but overcharge could be issue also.
    You didn't say if the problem occurred while driving at any kind of speed, if it is not happening then but only while stopped then you have fan clutch problem. With car idling and hot there should be a lot of air being moved by the fan, if not then bad fan clutch. If you have large electric fan then put it up to condensor and get good airflow across
    condensor, see if high side pressures drop significantly. Good rule of thumb, high side pressures should be about 2 1/2 -3 0 times ambient temp fahrenheit. If pressures come down to proper range, compressor belt does't slip, and cooling adequate once proper air flow established then problem solved.
    If pressures still high after good airflow across condensor then 1st bet is system overcharged, blockage in high side, stuck expansion vlv.


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