Compressor groan on 77 Newport/400 with ATC II

Later Model C Bodies - "The Formal Years"

  1. Pclancy

    Pclancy Member FCBO Gold Member

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    Truth be told, the compressor on my 77 Newport with a 400 has always groaned, but only when I use either the heat or the AC. Makes sense, I guess. And both the heat and AC work well.

    Lately, however, the groan seems to be getting louder (or is it my imgaination). Should I worry? Can I wait till it craps out or should I replace it now?

    (I met a guy at a car show once, he had I think the same year/model/engine, and I noticed his shiny new compressor (about half the size of mine which must be original). He raved on about it. Was it a Saginaw?)

    Any advice? What the best compressor to buy if I want to do that? What else should be changed while I'm at it? Or should I just put up with the not loud but noticeable groan?

    Thanks

    Peter
     
  2. Davea Lux

    Davea Lux Senior Member

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    Your stock unit is a RV2, Tecumseh compressor. Usually if they are "groaning" it is because it is low on oil and the end shaft bearings are starving for oil. Rod bearing is probably starving also. Some questions: Have you re-charged the A/C with R-134a? If so, check your charge. A low charge of 134a will cause the system oil to stop circulating and the oil will not return via the suction line to lubricate the compressor. This is something that will ruin your compressor. RV2 series compressors also lose oil over time from the front shaft seal on the compressor, as the oil is what creates the vapor seal on the front shaft. Small amounts of oil leak past the seal. This is more pronounced when running R-134a. If the unit is properly charged, add at least two ounces of "Pag" type oil to the compressor and see if it quiets down.

    If you have R-12 still in the system, you have the same problem and you need to add mineral type oil to the system once it has been properly charged. You will probably have to find a shop that still does R-12 work to add the oil because the pressurized cans of R-12 oil are long gone.

    You would do well to unplug the compressor so that it does not run until you determine the state of its charge as the groaning is a warning sign that the unit is stressed.

    The small compressors you referenced are rotary vane type compressors that are sold as a kit to replace the RV2 compressors. The vane compressors survive much better when running R134a. It is a fairly big job to convert to a vane type compressor as you will need fabricate new hoses and connectors. Once done this conversion is much more reliable than trying to run R-134a in a Tecumseh compressor.

    The other thing that could be causing a groaning sound is a failing clutch assembly on the compressor. Loosen the belts and spin the hub, it should turn freely without bearing noise. If the bearings in the clutch are bad, it will usually be noisy even when the compressor is off. A badly scored friction coupling on the clutch will also make lots of noise if it has started to slip.

    It would be better not to let the compressor fail completely as that usually will leave the system full of metal shavings that will need to be cleaned out.

    Dave
     
  3. commando1

    commando1 Old Man with a Hat FCBO Gold Member

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  4. Pclancy

    Pclancy Member FCBO Gold Member

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    Dear Dave:

    Thanks for such a knowlegable reply. Allow me to answer some questions and then ask you (and the others reading this) a few more of my own.

    The system is converted to R134a. I will check the charge level soon, but the vehicle is regularly serviced and I know (think) it was checked last summer (and the compressor was groaning back then as well).

    So assuming my system is charged, and assuming adding two ounces of pag type oil does not quiet the compressor down, then I assume my compressor has issues, correct?

    I guess the first decision is whether I convert to a Sanden type compressor, per the link that Commando 1 sent or just rebuild my current Tecumseh.

    I am NOT a mechanic, and I fear the complexity of a Sanden conversion. But I will do that if everyone feels that's the best solution. What do you think of simply going to the Original Air Group and having my current compressor rebuilt? And while I'm at it, checking all the other components--evaporator and condensor--to make sure they are up to snuff?

    I seek the simplest solution, even if that costs a bit more.

    Finally, since it's winter here, I don't use the AC. But the compressor runs even when I just use heat, and so I assume that given the groaning, this is not somerthing that should wait?

    Thanks,

    Peter
     
  5. LeBaron1973

    LeBaron1973 Senior Member FCBO Gold Member

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    Since your car has the ATC II system it makes sense that the compressor is always on so the temperature can be constantly adjusted to your desired setting.

    Considering the potential for $$$$ if metal shavings pollute your system I suggest you disconnect and thoroughly check it out as Dave A. Lux has suggested before anything occurs.

    Best wishes with it.
     
  6. cantflip

    cantflip Old Man with a Hat FCBO Gold Member

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    The compressor runs when you use defrost so the evaporator can dry the air before it goes to the windshield. The advice to unplug it until it can be looked at is very good advice. The fact that it has been left to do this for so long is troubling, but it isn't a conclusive indicator of a damaged compressor... just an unhappy one.

    You may get lucky and a proper oil charge is all she needs to go for sometime longer. Now that she is on R134a refrigerant, there should be at least an annual checkup. Most newer techs are completely unfamiliar with these, and I must admit... my experience with them is limited as well.

    You did buy an FSM a while back IIRC. There will be a set of instructions there for checking the oil in the compressor. This is shop work, because it involves discharging the system. The recommendation to add a couple oz. of oil to see if it clears the noise is more diagnostic than repair.

    The 2 issues working against you without draining and fully refilling the compressor are:

    1- contaminated oil, caused by an improper conversion to R134a by whomever did the job

    2- low refrigerant oil caused by leakage and/or improper filling procedures.

    These compressors have an oil sump and take a lot more oil than more modern radial designs. It wouldn't be at all uncommon for a tech to not find or not follow the directions to check/fill the oil in one because it would be completely different from their experience with any newer design.

    More simply... just disconnect the compressor clutch electrical plug, and you can run without the compressor without (much) risk of damage. A bad bearing on the pulley would be the only concern left, you'd know, because it would make terrible noise and eat the belts... immediately.

    Review your FSM and offer it to the shop who is doing the work for you. It helps to understand the repairs, but doesn't help to get too overbearing with a tech... if they think you're crazy, you may need a different tech. I would expect them to be open minded when you express the concern and show them the procedure in the book.
     
  7. commando1

    commando1 Old Man with a Hat FCBO Gold Member

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    Then that would be to just replace the compressor with a rebuilt unit and replace the dryer. This will set you back 500 bucks.
    See if your happy with it. If not, take it to the next level.
     
  8. Davea Lux

    Davea Lux Senior Member

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    You should unhook the compressor until you can get it looked at. (There is a blue wire coming off the compressor that has a detachable plug about 6" from the compressor) A rebuilt compressor is the easiest and cheapest fix if the compressor is failing, but these compressors do not have a real good track record when running R-134a. As long as you have the A/C serviced every spring, you should be able to get by. If it were mine, I would probably unhook the compressor during the winter months. Operating gas pressures drop in cold weather which is when most compressor burnouts occur due to the lack of oil circulation.

    The Sanden conversion is a more permanent fix, but it will set you back some serious bucks if you have it done. You are probably looking at somewhere in the neighborhood of $1200 or better. If you are planning to drive this car a lot and are not worried about a fully stock restoration, the conversion might be a better choice for the long run.

    Dave
     
    Last edited: Feb 13, 2018
  9. Pclancy

    Pclancy Member FCBO Gold Member

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    Dear Dave and others,

    Thanks for the superb advice. I took it to my trusty Chrysler doctor, who knows the car well, and indeed the compressor was seriously low on both r134a and oil. He corrected both conditions, and the compressor now runs without much noise. AC and heat seem to work just fine. I will report back later if problems occur. A lesson learned. I thought I was keeping up on general maintenance, and now realize that this beast is just full of surprises. In any case, off to the next adventure.

    With many thanks,

    Peter
     
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