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  • Restriction?

    66 Chevy C10,
    Factory TXV system,
    134a,
    Aftermarket A6 compressor replacement, (S6, Pro6TEN)
    New Parallel flow condenser, hoses, TXV, evaporator and dryer,
    Low side: 20-25,
    High side: 250-300 and climbing,
    80-90 degrees ambient,
    @1,500-2,000 RPM
    Electric radiator fan and 3' diameter fan at grille.

    Based on the pressures and the lack of cooling could be a restriction? Everything is new so I doubt there's debris causing the restriction. Compressor has no abnormal noises. Could it be the TXV? I did a search and saw that a slow pressure equalization after turning off the system is an indication of this. After turning it off the low side immediately goes to 70ish and eventually goes to 90ish, but the high side is extremely slow to fall. After several hours it's staying at 150 psi. The sight glass is all bubbles/foam when running just for reference... I know you can't rely on it for a charge indication.

    The TXV is buried inside the evaporator case so I want to make sure if there is something else to look at first.
    Last edited by 69-er; 10-16-2019, 06:46 PM.

  • #2
    Over charged? Also was that originally a POA or not? What controls the evaporator frost?

    Comment


    • #3
      No POA. It has a thermostat switch with the bulb mounted on the evaporator fins.

      I don't think it's overcharged. I calculated the 134a charge based on the factory amount. I believe I initially charged to under that and started creeping up on the calculated amount. Although I believe I may have added a little more just to see if it would help.

      Comment


      • #4
        Should be 70-80% of R 12 amount by weight. Is the condenser shedding the heat? can you grab the outlet and its not too hot? Should be slightly warmer than ambiant but not too hot to hold onto.

        Comment


        • #5
          Thanks! I'll try that.

          I was also able to finally get the search terms right and found a few posts similar to mine. You have several tips and advice there I'll be trying.

          Comment


          • #6
            Update:

            The assembly manual states 48oz R12. I charged it with 40oz 134a. I initially started at the lower end and crept up to 40oz.

            Static pressures still didn't equalize after 2 days. 85 and 125.

            This time I noticed soon after starting the system the low side almost went to 0. The high side immediately climbed towards 200. Vent temps, feeling by hand, actually felt cool.

            After stabilizing pressures were 20 and 300 and climbing. Vent temps warm.

            The condenser outlet is almost as hot as the inlet. Can touch it for less than a second.

            Sight glass foamy.

            After stopping test pressures initially stabilized at 115 and 400. 30 minutes later 110 and 275.

            I forgot to mist the condenser to see what pressures would have been.

            Evaporator outlet going into compressor very warm, not cold like I believe it should be, correct?

            Comment


            • #7
              69-er: Quote ">
              After stopping test pressures initially stabilized at 115 and 400. 30 minutes later 110 and 275.<"

              Huh? How can that be? Somewhere around or before 400 system should blow out or blow up something.

              For now I question all measurements, tools, gauges and maybe what gas was used and how? Acme (134a) fittings and connections are not all cooperative, on vehicle or the hose ends of gauges. Double trouble. Add the pressure locking ends now a couple years of those are ruining the show with all intentions to save the world over a spit of lost refrigerant.

              IDK - I suggest start all over charge from a well held vacuum charge to your guess as best you can without allowing air in even a hose not bled out.

              Other: A/C anything is over where I am. The tools and things have to be out of my way in prep for Winter mode here. BTW did notice Home Depot no less has 12oz cans of pure 134a might just be the one closest to me not others but was just $4 bucks a can down from almost $18. I can and will use the small cans if only they aren't heavy to move all over the place just take serious care to run thru gauges (two sets if need be) get the correct or intended weight wanted.

              Your parts are new as stated IMO haven't proved themselves to be good yet adds to the pressures being all over the place just can't know if those are right or not quite yet?

              Tom
              MetroWest, Boston

              Comment


              • #8
                Not getting the heat out at the condenser, or non-condensable gas (air) in the system. even on 100 deg days I can grab the outlet of the condenser and hold on, temp around 120-130.
                Check that you have good air flow thru the condenser, and that the fans aren't fighting one another. Does the engine have a mechanical fan? Are you sure you got all the air out with a vacuum pump before charging?
                Until you solve the hot gas at the condenser outlet everything else is moot. How big is the condenser you replaced compared to the replacement? Not talking rated capacity but physical size.

                Comment


                • #9
                  Tidbit from top post? ">
                  Electric radiator fan and 3' diameter fan at grille.<"

                  Just what is that? 3 FOOT fan?
                  Tom
                  MetroWest, Boston

                  Comment


                  • #10
                    I think he meant a 3' fan on the garage floor pointing at the grille.

                    Yes, R134a cans are reasonable at Home Depot and WalMart. Many have the "new" special top on the cans now.

                    Comment


                    • #11
                      New Cans: Yes that new @#$% tap is supposed to self seal when a tap removed even the dull one it's just a flap. I'm waiting a kid could do that with a pen! That one with a hose the hose end doesn't purge out. I use a low side retrofit blank or union to go to gauges, yellow hose need be. First one did quite the show spinning around the tarmac here didn't sea too well dangerous as all get out but our fearless EPA says it's saving the world so who am I?
                      Tom
                      MetroWest, Boston

                      Comment


                      • #12
                        Originally posted by Tom Greenleaf View Post
                        69-er: Quote "&gt;
                        After stopping test pressures initially stabilized at 115 and 400. 30 minutes later 110 and 275.&lt;"

                        Huh? How can that be? Somewhere around or before 400 system should blow out or blow up something.

                        For now I question all measurements, tools, gauges and maybe what gas was used and how? Acme (134a) fittings and connections are not all cooperative, on vehicle or the hose ends of gauges. Double trouble. Add the pressure locking ends now a couple years of those are ruining the show with all intentions to save the world over a spit of lost refrigerant.

                        Your parts are new as stated IMO haven't proved themselves to be good yet adds to the pressures being all over the place just can't know if those are right or not quite yet?

                        Electric radiator fan and 3' diameter fan at grille?
                        Yes, extremely high. I don't remember seeing a relief valve on the compressor. The trinary switch did cut off the compressor around the time it was approaching 400. It rose on it's own to 400 after the shutting down the engine then started dropping.

                        I haven't had problem in the past with my equipment. I'll look into that.

                        Since I was initialy thinking it's the TXV I was figuring it could be bad from the start. I never bothered to try to ice water test it first. I can't test while running as it's buried in the evaporator box uness I can remove the top without removing the box from the firewall.

                        What about the low side approaching 0 PSI? Isn't that an indication of a restriction between the TXV and the suction port of the compressor? Plus, the guages never do equalize.

                        Correct, a 3 foot floor fan pointed at the grille.
                        Last edited by 69-er; 10-21-2019, 03:45 PM.

                        Comment


                        • #13
                          While I can't rule out a restriction problem, it is secondary to the fact that you are not getting the heat out at the condenser.
                          Lets say you had a shut off valve on the outlet (evaporator side) of receiver, what would happen? The compressor would compress any gas left between the inlet of the evaporator and the compressor, the condenser (if working correctly) would remove the heat, and the refrigerant would be stored as liquid in the receiver. In short, there would be a short rise in pressure, followed by a leveling off as no more refrigerant is making back to the suction side of the compressor.
                          That is not what you are reporting. In your readings the pressure continues to rise and the outlet of the condenser is hot. What this tells me is the refrigerant is being heated by compression, the condenser is NOT getting the heat out, the refrigerant is then sent on its way hot, it flows thru the rest of the system and get compressed again gaining more heat that is not removed, and continues to build until the system blows a safety valve or a limit switch shuts the system down.
                          While you may have other "hidden" problems the 1st order of business to get the heat out at the condenser, the outlet should be slightly above the temp of the air passing thru it. 10 deg over would be good, 25 deg acceptable Until you can get that, everything else is moot.

                          Comment


                          • #14
                            Oh, and to explain the low side readings. If the condenser isn't getting the heat out, and the refrigerant is boiling in the liquid line, the Tx will being metering vapor instead of liquid. the same volume of liquid will boil to a huge amount of vapor, where as the same amount of hot vapor will contract when cooled after the restriction, In short you can't pass enough vapor thru the Tx valve to keep up the capacity of the compressor. ergo low pressure readings. It is one of the reasons pressure readings alone can't be used to asses the system.

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