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Poor cooling suddenly?

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  • Poor cooling suddenly?

    I hope someone can help me.

    1988 Buick, Electra Park Avenue, clutch/orifice tube system. Converted to R134A 15 years ago.

    Cooling was great yesterday at startup when driving for 5 miles and the suddenly very poor/no cooling.
    Under normal working AC system interior center vent would give 38 - 42 degrees F output air

    Checked today.....
    Ambient 88 degrees F, 42% humidity

    Static pressure: Low side - 98 PSI, High side 98 psi.

    Testing conditions………

    Idling at 600 rpm, AC clutch engaged.
    After 10 minutes of operation, windows open, blower on high, AC temp set to 60 degrees F, radiator cooling fans on

    Accumulator temperature - 68 degrees F
    Evaporator temperature - 69 degrees F
    Interior center vent temperature - 68 degrees F

    Low side pressure - 60 psi
    High side pressure - 160 psi

    Test data with engine speed raised to 2000 rpm for 5 minutes...….

    Accumulator temperature - 59 degrees F
    Evaporator temperature - 64 degrees F
    Interior center vent temperature - 60 degrees F

    Low side pressure - 40 psi
    High Side pressure - 275 psi

    Any suggestions on what may be wrong?

  • #2
    Is the compressor clutch cycling? If not you could have a bad (leaking) valve in the compressor or a slipping clutch. From you description I don't see where you messed with the charge amount, good! Hard to diagnose this type of problem over the net, It seams like the compressor can't draw the low side down low enough.
    Normally if this was a problem that slowly came on, it would have more possible causes. Where it was working fine, then the next day is not, it is unlikely a refrigerant loss or low charge are to blame, esp if the clutch is not cycling, it is more likely to be the compressor itself.
    I would have a shop look at it rather than take a gamble and throw expensive part at it.


    • #3
      Thanks for the reply!

      The clutch is not cycling, it is always engaged (compressor pumping). With cold engine, first turn on of the AC no improvement of getting cold air out of the vents over a 5 minute period., vent air temp is about 65 to 70 degrees during that 5 minute period. I assume that the clutch would only cycle when the evap temp was low enough?

      The clutch pulley bearing on the compressor is rough sounding so that is shot. I heard a few compressor clatters when running. Plus the drive belt squealed a few times with maybe the compressor locking up.

      I ordered a new compressor, accumulator, orifice tube. Hopefully the old orifice tube doesn't show any metal particles. Trying to break the line fittings on a 32 year old system will probably just not work to flush the system. Does flushing the system from the evap at the accumulator, through the condenser to the detached compressor line, and from the orifice tube down to the compressor detached line sound logical?


      • #4
        At very least, you need to separate the liquid line at the orifice tube and inspect the screen on the tube. Failure to remove any debris in the system that can then circulate back to the compressor, can ruin the new compressor. Then you have to do the job all over again.
        If I had any question, I would replace the condenser. Not only are they hard to clean, they are subject to damage from road debris and de-icer sprayed on the roads.
        It is your eyes on the system, you have to make the call.


        • #5
          This is my 94 year old father's Buick. He drives it about once a week, never sees salt and very rarely any rain. The car looks new, the engine looks new. I had to add about 1 can of R134A a year in early spring after it sits during the winter. I realize that the car sitting for months during the winter does nothing to lube the compressor shaft seal. I try to run the car in the garage at least once a week in the winter. With the defroster on it will cycle the clutch on and off.

          This is why I'm thinking of flushing the system after the lines a are broken at the accumulator, the orifice tube, and at the compressor. I should be able to do it good. If I see no debris at the orifice tube screens then maybe no flushing is required?
          Last edited by Fussybob; 1 week ago.


          • #6
            OK flushed the complete system, replaced the compressor, receiver/drier, orifice tube all o-rings, 8 oz of PAG150 oil.. Pulled the vacuum for an 2 hours, let sit for 1 hour and no leaks. Put in 30 ounces of R134A ( calculated from GM's R12 to R134A conversion information). Runs great! Today it is 90 degrees F ambient, vent temperature is 40 degrees F, this is at idle, sitting still in a garage.

            Now I have a problem where I removed the receiver/drier low side port schrader valve core as I was putting on an R134A service valve adapter with its own core and said why do I need 2 cores in series. Well when I went to remove my low port service hose from the low port valve the freon along with some oil shot out, I immediately put the service hose back on and determined that the the low side port adapter doesn't have a core valve in it!!! I need to purchase a new adapter valve with a core and try to switch this very quickly. Any one have any suggestions on any way to do this switch without losing my freon/oil charge???


            • #7
              If it doesn't have a core, there is going to be no way to take your hose off and change the fitting or install a core. There are tools that let you swap out cores without a loss of charge, but you need to have that special tool on the fitting before removeing and replacing the core. ANy attmept to remove the hose will result in a total loss of charge.
              You don't want to leave the core in the R 12 fitting either, Two cores in tandem will not work either.


              • #8
                The R12 to R134 port adapter (made the conversion in 2004) didn't have a core just a spring loaded pin that pushed against the core in the accumulator. I didn't know this and removed the core from the new accumulator believing that the old conversion port adapter that I reused had a core in it. Well this is what I did, I quickly removed the service hose, and quickly screwed the cap on the adapter (wasn't that hard to do system static pressure was 70 psi), removed the adapter and then quickly swapped to the new adapter with a core. I had some freon loss and minimal oil loss as I had a white sheet covering the engine, my oil has a dye in it so there was only one small area of dye on the sheet. My service hoses are 5 feet long I had them off and on a few times so I lost some freon there. I had 4 ounces of freon left in the can that I originally filled the system with, so I just added that amount. A/C works just fine. So yes you can swap ports and lose not loo much freon if you are fast enough!!!