Expansion valve failure?

Heating / Cooling / AC

  1. Early a body

    Early a body Well-Known Member

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    I know this is a body forum but have a b body question. Have a 383 in a 66 charger I converted to the original air stage one mopar kit, basically the engine compartment stuff. Had the heater box professionally rebuilt. All in the past 5 years. Out of the blue it started blowing warm air. Hooked up the gauges noticed the readings were the same at 100 on high and low.

    Swapped out the compressor- same issue happened. This time the gauges read lower but still even. Here is the weird part. If i let the car sit or i start it first thing in the morning, the a/c blows cool. After the car warms up or i turn it off then back on again it blows warm air.

    The expansion valve ices up pretty good when its working, stays room temperture when its not working.


    So since I replaced the compressor- the expansion valve is bad?

    I have bypassed the heater control valve on the firewall - it was not holding back all of the coolant , i will send out to rebuild

    I had the system evacuated and recharged by a professional mechanic with a machine. After i replaced the compressor they put 2.5 pounds in the system.

    I brought it back to them to discharge so I could replace the expansion valve- they removed 2 pounds- so my guess is the expansion valve is sticking? there are no leakes in the system - dye and uv light test confirmed that.

    anyone else have any suggestions. Plan is to replace the dryer and expansion valve
     
  2. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    Why did you replace the compressor? Did it go bad? When they fail, they can puke all kinda nasty through the system. The two main places debris gets caught? Expansion valve and drier. Sometimes the condenser too.
     
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    • 70dart340

      70dart340 FABO Gold Member FABO Gold Member

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      It sounds like your filter/dryer is plugged up, or your TXV valve is plugged. Did you change those out? Icing also suggests an overcharge of refrigerant. What are your high and low side pressures at ambient temperature. I'm not an expert, but I've done a few A/C systems.
       
    • Lefty71

      Lefty71 Well-Known Member

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      With the compressor running?? That's very odd. I would look to the compressor as problem. If the compressor was not running, then I would look for the reason why. As far as the dryer goes, it should always be changed anytime you tear into any refrigeration system. If you indeed have a restriction otherwise, you need to find it.... but it sounds like you are saying the problem is dynamic?? If so, then yes the expansion device (or TXV) is failing and should be changed. Just make darn sure you have taken the heater out of the equation somehow. Make sure to evacuate and recharge with the proper amount for the new or bastardized system. Also, putting 2.5 pounds in and removing 2 pounds is what we call leaking lol
       
    • RedFish

      RedFish Well-Known Member

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      The expansion valve should have a screen inside the ingoing port. Might be stack of 2 of screens, might be 5 of them. You can pick them out of the port and clean them but, you might do this over and over again. No way of knowing how much debris a failed compressor put in the system. You might think flushing the system will remove the debris. Maybe not. When I worked at a Ford dealership a new F150 had compressor failure . Warranty paid for compressor, system flush, new drier, new fixed orifice ( replaced expansion valves in later models ). Then everything except the compressor repeated 4 times in 3 months. Fixed orifice totally blocked every time. Customer was very pizzed. Warranty finally paid to replace entire system, hoses and all. Everything we removed had to be shipped back to them so if a faulty piece of hose was the root cause we would never know it. Better luck with yours.
       
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      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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        A system that works and then quits --- many times has WATER (humidity) in the system. You may have a contaminated dryer, etc. I would pull and either "bake" or replace the dryer and CAREFULLY re-evacuate and re-charge and try it again

        What happens is "when stopped" for a period the ice goes away and the system works, as the system is operated, the water circulates until it freezes at/near the orifice/ TXV and then clings and grows as more forms, then at some point plugs up the port
         
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        • 70dart340

          70dart340 FABO Gold Member FABO Gold Member

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          The system needs to be completely evacuated under vacuum before any refrigerant is added. I always assemble the system, apply vacuum. and leave it overnight to check for leaks. The system needs to be completely evacuated of non condensable materials. A new filter/dryer is a must. While the system is under vacuum, be sure to rotate the compressor by hand to ensure all passages have been exposed to vacuum to ensure all the moisture is removed. It's not as hard as it sounds, and many auto parts stores, like Auto Zone, will loan you a vacuum pump. The moisture must be removed from the system, as 67Dart274 recommends, is correct for maximum efficiency. If you have problems, post again. There are many experts on this site who'll help you.
           
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          • 67Dart273

            67Dart273 FABO Gold Member FABO Gold Member

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            And now.............yet another annoying story from the old days

            After I had swapped a 340 into the old 70 440-6 RR.....the car had had an aftermarket "knee knocker" A/C system, which of course would not fit the 340. ..............Until one day I took the rather large compressor mounting bracket and discovered that a couple of simple mods and some different water pump bolts and spacers---------and it fit!!! And so did the "stack on" crank pulley!!! This system was connected with hose clamps---------from the supplier. I decided to "go for broke" and had stored it with everything pretty well plugged off. So I reinstalled all of it and got the engine bay nice and hot (to help boil off moisture).........not difficult in a San Diego summer...........BUT I HAD NO VACUUM PUMP. R12 was cheap so I bought a few extra cans. I "swept" the system with a couple of cans, then USED ENGINE VACUUM (LOLOL) to evacuate it. I still laugh about this. IT WORKED!!!! The system still worked for several more years until I sold the car
             
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            • 67Dart273

              67Dart273 FABO Gold Member FABO Gold Member

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              On a side note, realize that moisture "boils off" in a vacuum because the pressure is so low......just like "driving up" to Denver causes water to boil at a lower temperature. When you get down into the "lower reaches" approaching 28" Hg and lower, water will boil at it's "normal" freezing point!!
               
            • Demonic

              Demonic Well-Known Member

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              Well, hopefully that is true. The shaft seal is a likely leak point if it is very old. The commercial/industrial method is to pressure test a system with nitrogen, have it hold 300 psi for a day or so, and evacuate to 400 microns and hold that for a hour. A/C is detailed, precise work. More info would give a more exact reply.

              How Long Should You Evacuate a System?

              What is a Micron? - HVAC School

              http://www.jbind.com/pdf/Pump Presentation Pump and DV.pdf
               
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              • RustyRatRod

                RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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                "Annoying stories from the old days" You need to write that book.
                 
              • Demonic

                Demonic Well-Known Member

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                Wrong. So your refrigerant temperature is dropping below 32*F perhaps. Imagine whats happening on the evaporator. Ice can form, even in Nevada if it's humid enough. Then it can eventually block the airflow. What is your suction pressure? The goal is a 36* to 43* evaporator.
                 
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                • 70dart340

                  70dart340 FABO Gold Member FABO Gold Member

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                  If it's icing, your charge may be too high, or another problem in the system Buy or borrow a good set of gauges, download a good TPR chart, and go from there.
                   
                • Early a body

                  Early a body Well-Known Member

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                  Today I disconnected the line from the dryer to the expansion valve and noticed some crud in the hose. Cleaned the hose out with some a/c flush solvent took out the dryer and looked inside and saw a bunch of crud. Took off the expansion valve and bunch of crud at the inlet and some on the outlet side. I tried to see if I could get air to go through the valve and no air would go through. Warmed up the end of the valve with a heat gun too see if it would open and it would not open or is filled with crud. Good news is all the other lines and evaporator and condenser were free of crud. So it looks like the crud got stuck in the expansion valve clogging it up. I am guessing the dryer was the main cause.
                   
                • 67Dart273

                  67Dart273 FABO Gold Member FABO Gold Member

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                  Icing evap is usually not overcharge, but under. Overcharge raises evap pressure and temp
                   
                • 70dart340

                  70dart340 FABO Gold Member FABO Gold Member

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                  True that, but if his capillary tube is blocked, or his TXV is bad/plugged, it causes similar problems. I bet if you and I were there with our equipment, we'd have it figured out in 2 hours. Much respect to you.
                   
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