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High pressure on the low pressure side of the AC System.

Discussion in '80-Series Tech' started by BadgerManBEN, Jul 29, 2009.

  1. BadgerManBEN

    BadgerManBEN

    Messages:
    51
    Location:
    Salt Lake City
    My AC stopped working so I checked the compressor and it seemed to be working just fine. So I went and picked up some R134a with the gage on it thinking it must be time for a recharge. I plugged it in to the low pressure side, even made sure it was the low pressure side by tracing it out, and the gage read 130psi. If I am right that is 100 psi too high. Anybody heard of this and have an idea what might cause it?
  2. BadgerManBEN

    BadgerManBEN

    Messages:
    51
    Location:
    Salt Lake City
    Other details that may help. I saw the high pressure and did not try to discharge any freon into the system. It was high pressure with the engine running and while it was off. I let some of the pressure out down to about 100 psi and it went back up.
  3. Tools R Us

    Tools R Us Moderator SILVER Star

    Messages:
    17,429
    Location:
    Chandler, AZ
    Was the compressor running? If the compressor isn't running the low and high side pressures will be the same, base system charge, about what your seeing.
  4. 1972FJ55

    1972FJ55

    Messages:
    703
    Location:
    Tucson, AZ
    Is the compressor engaged when you're checking it? Look at the front hub of the compressor, not the pulley, and see if it's spinning. If not, then the pressures will be even on both sides of the system. By the way, those hose gauges are notoriously inaccurate.
  5. dixie_cragger

    dixie_cragger

    Messages:
    343
    I had my AC converted to R134a in my FJ62. It wasnt until my AC went out a second time did we realize the fittings were flopped from the conversion (hi pressure fitting was actually the low pressure side and vice versa). I do believe the AC shop was able to insert freon into the hi pressure fitting side....
  6. BadgerManBEN

    BadgerManBEN

    Messages:
    51
    Location:
    Salt Lake City
    Yes, the compressor was engaged it wasn't just the pulley spinning. No modifications have been made.
  7. FJ60Cam

    FJ60Cam SILVER Star

    Messages:
    3,385
    Location:
    Memphis, TN
    Yep, you can fill on the high side. With the engine off, turn can upside down and fill as liquid.
  8. TX Cruiser

    TX Cruiser

    Messages:
    622
    Location:
    Austin, TX
    Knowing how these compressors don't internally disintegrate, I'd recon the expansion valve is stuck open. 130psi is a bit much when the pressures are equalized with the system off, so this tells me the compressor is pumping. That is unless your ambient temperature is really high. Put a real set of gauges on it and holler back. The valves in the compressor could be shot, but not likely.
  9. roneyj

    roneyj

    Messages:
    49
    Location:
    Chandler, AZ
    If this was the gauge that comes with a can for around $15-$25, its junk. I return about as many of these as I sell. I would not add or release anything untill you check it with a real set of gauges. Just me experience.
  10. BadgerManBEN

    BadgerManBEN

    Messages:
    51
    Location:
    Salt Lake City
    I had a friend mention, who is a pretty decent mechanic, say that the system may just need to be balanced. Anyone ever hear of this?
  11. TX Cruiser

    TX Cruiser

    Messages:
    622
    Location:
    Austin, TX
    Balanced? Never heard of that. Might he have said that the pressures are equalized?

  12. popawoody

    popawoody SILVER Star

    Messages:
    22
    Location:
    Redondo Beach, California
    "Balancing" in A/C biz

    The term "balancing" is a term sometimes used in the refrigeration business that referrs to adjusting the level of charge. It's a pretty arcane term, but it's more accurate than "charging" since sometimes the system is overcharged. A refrigeration system is properly charged by adjusting the referigerant level so that the evap is producing the correct amount of superheat for the particular referigerant and expansion valve. Superheat is the measure of how much heat is being transferred. The technical details aren't important here.

    Your friend had no great insight I'm afraid. The best advise I can give is the same as that given by others here. Put a REAL gauge manifold on the system so you can see both suction and discharge pressures. If the suction side is, indeed, standing at 130psig with the compressor turning -- and the high side isn't off the charts -- then either the compressor valves are leaking badly (which isn't too likely) or there's a pressure relief valve in the compressor that's open.

    Buy, beg, borrow or steal a set of gauges before you do anything else.
  13. TeeDiggs

    TeeDiggs SILVER Star

    Messages:
    333
    Location:
    Missoula, MT
    Does anyone know if places rent out real gauges? I completely just bought a $19.99 hose gauge from AutoZone. :frown: Havent used it yet, but they did have a Manifold Gauge for I believe $39.99 in there... would that be worth anything?
  14. e9999

    e9999 You want to do what...? Moderator

    Messages:
    15,143
    Location:
    PRK
    if you buy an A/C manifold and gauge set, be sure it has the QD connectors for 134. Those are not that easy to get separately and are expensive.
    HF has a set for car systems that they have regularly on sale for about $40 with the QDs. Don't know how accurate.
    Not all inexpensive gauges are bad, though. I have a pro Yellow Jacket manifold type set and it was pretty close to what my cheapo Kragen filler / gauge set was indicating.

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