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Geo Tracker short cycling

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  • Geo Tracker short cycling

    I have run into a problem and hope someone can suggest a solution. I know just enough to get in trouble otherwise.
    I bought a 1996 Geo Tracker.Sanden SD7B10. It blew pretty cold air at idle sometimes but not at 30mph or above. Then a hose blew wide open. As briefly as possible-Hose replaced(low side at compressor), another leak fixed.Replaced schrader valves and o-rings for parts removed. Replaced dryer. I removed and emptied the compressor which had only a 1/4 oz of oil. There was a lot of oil under the hood though. Pulled vacuum. Added 90cc Pag oil specified to the compressor. Began to add 3lbs 2 oz of R134a as specified on badge under hood.

    I was using a 30lb tank through a manifold with a scale under the tank. When 1 lb 6oz had gone in the compressor began to short cycle and the refrigerant stopped going in. The manifold showed 50 to 60 on the low side which dropped slightly when the clutch cycled off. The high side ran 400 to 450.

    I hope I have provided the right information. Is there a valve or a sensor that would cause this? It runs wirh a reduces fill of 134 but not enough for our South Florida heat and a black convertible top.

  • #2
    Two thoughts, something cause that hose to blow, and 3lbs, 2 oz sounds like a lot for that small a car.
    Let me get this right: the low side DROPPED when the clutch cycled off? Way too high on both the low and high sides. I say you have a plug somewhere or a completely useless condenser.
    You are going to blow something else if you don't shut the system down until you find the problem. Blocked condenser, blocked metering device (Tx or orifice tube) or some other blockage in the system.

    Comment


    • #3
      Somehow "Tracker" is missing from my paper chart. No chance this holds 3+1/2 POUNDS of refrigerant unless it's some bus version or something? Anything using 134a and moreso with OBDII in 1996 models (all of N. American versions) would shut down by high side pressure or should. Ratings for hose and parts wouldn't take the insane pressures and if it didn't shut down high bet would choke compressor.

      If you wish to tweak this and it's not still in need - maybe lots more? I'll try but need system known capacity both oil and refrigerant. Any take so little tweaking them by the seat of your pants is a real pest all are very fussy to be within 5-10% of a known charge or things go wrong,
      Tom
      MetroWest, Boston

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      • #4
        I seeing places on the net that say 1.32 lbs of 134A and 3.2 oz of oil, all of which sound a lot more reasonable.

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        • #5
          Originally posted by RalphARoni View Post
          Began to add 3lbs 2 oz of R134a as specified on badge under hood.
          Don't I see this R134a capacity as 21 oz.??? https://www.ericthecarguy.com/kunena...er-ac-recharge

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          • #6
            I have never seen that much go into a tracker! Please double check your charge specification.

            Comment


            • CJB
              CJB commented
              Editing a comment
              I also see 21 ounces of r134a specified as the max charge for the 1996 Tracker. The oil quantity is 3.5 ounces of PAG 100.

          • #7
            Anytime I see high pressure I usually first suspect condenser airflow problems. This usually comes in the form of a bad fan clutch, or electric fan in the case of a front-wheel drive vehicle. I don't see overcharges as much in the shop, but, I see it occasionally. I see excessive oil charge more than excessive refrigerant charge. Fan problems is what I see the most. Dirt between the condenser and radiator is also something to look for. 1 lb. 5 ounces is what I have for max charge in my reference guide.

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            • #8
              In older stuff I often see degraded condensers, where the tube to fin bond is compromised and little or no heat transfer takes place. The condenser may look good visually, but in terms of heat transfer from the refrigerant to the air, it is bad. It is easily tested with a mist test.

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              • #9
                I am really .embarrassed! You guys are right. There is an under-hood sticker and I checked it for 134 capacity. My eyes are old and the printing is worn and I mistook the 3.2 oz PAG capacity for 3lbs 2 oz of 134. The actual amt of 134 is worn off but now that I have taken a picture and enhanced it I see that it should have been 1lb 4oz perhaps. I found a site that stated 18oz. I removed refrigerant to 18oz and it works fine. Thanks for the answers. I'll try to get it right next time.

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                • #10
                  Did you find a "smoking gun' as to why the hose failed in the 1st place? Could be a simple as vibration at the compressor, but I would like to know it would not happen again.

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                  • #11
                    RalphARoni and Anyone reading:

                    Glad you found anything! Charts about always state to refer to under hood info/stickers or markings from last person there with things known. Mark it again YOURSELF info gets lost, fade like you found. Parts replaced. I've had luck with "Silver" metallic Sharpies do take being wet, write on dark things AND can remove that with carb cleaner and a paper towel if wanted or info changes.

                    This case mark that hose was done date and miles. It's really good info later if not you the next person how long something lasted if reduced to some guessing really saves time,

                    Tom
                    MetroWest, Boston

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                    • #12
                      I like Paint Pens for reliable marking. See Michaels, Hobby Lobby, maybe even Ace or Home Depot if you look in the right aisle.

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