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Faulty Expansion Valve?

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  • #31
    When I use a generic replacement condensers, I go for the biggest (highest capacity) unit I can fit, even if the ton rating is well above the system capacity. I know some will push back on this approach, but it helps when the air flow isn't quite as good (like not sealing to the radiator and air goes around not thru) and the added capacity just becomes liquid storage when not needed.
    The result is lower head pressure and sub-cooling of the liquid (cooled below condensing temp) all of which helps.


    • #32
      First photo with the auxiliary fan off, engine at 1500 rpm's:

      Click image for larger version  Name:	qKHq-HoOl--xwkZ9s8RfuKIOGI8ANgcCagPBctFqn544JASAkGHy3L3kkmFYYsv_XhDkY12iOfOx38JwJH2PBLfYpt7gaLSGpSFjxtWsIzHAT2XJy4QGhGkcvhUtYYLT-V_fDb5z7NvBobUbLYbUJm7NETO0KYax5AVF_gFiTz6ii72rmuw-35jucGjQIOCIKUltUtbbysy59R-qTDIlxrXgyyyHUyYzXZBrav6jdt_hEoP3lOra47NgjxCKQxy Views:	1 Size:	141.9 KB ID:	1909

      And the second photo, same RPM but with the pusher fan running.

      Click image for larger version  Name:	Ztnw4ZlcVyjOkE1uRl3Hw9QKMLnvIqo6omL0yZRwsI5p7_jcU2oMzEClcNPfRPQ7v0QMGgWq77Capw2dbH1Y1ROqT1SiotiVB94wz8vaA4-4AnqiQnZz-Oz2b8wv1xbaEu_xfl8Q3ipS899LtEJR5sjeUH3e3kwEBZOJ30vXlcR_lc6W1O4yD1BPru4-ACpCxMo4rhGYF6h4ltDZfoSyYLqw5FkqzaMgg5dB6F9s9Wtv9Zu4ANCvQREny577iyq Views:	1 Size:	117.8 KB ID:	1910

      One thing that I think is going on is that I'm getting varying high-side readings due to the constantly-variable viscous coupling on the engine's mechanical fan pulling varying amount of air through the condenser, especially with the pusher fan off. One moment, it's really putting out the air and then it catches up and puts out much less.
      Anyway, I was getting 44° vent temps with the fan on 2 and 90° ambient temps in front of the condenser at 1500 RPM, so I'm pretty happy.
      Last edited by Wren; 06-15-2019, 10:45 PM.


      • #33
        Wren: Bear with me the site is showing last two posts by you are not visible? Shows it's now working with pics of gauges. Sorry for the site trouble trying to find the button to make those show. Looks good if it takes a while a site issue unknown to me,
        MetroWest, Boston


        • #34
          Pressures look good to me, I'd look to see if the air handling side can be improved, Is the heater valve or door shutting off all heat into the air stream? can any air bypass the evaporator and not get cooled?
          Don't know why your last post needed to be "approved" But should be showing now,


          • #35
            The heater valve is working properly. 240's are known to have issues with the heater valve, but this one is good.
            There is potential for some shrouding around the condenser that would direct more are through it instead of around it. This car is getting a turbo engine in the near future and we'll probably tackle that when fitting the intercooler.
            Regarding the message needing approval, I received a popup that said it was flagged as potential spam when I was doing some editing.
            Thanks for all the help with this car.
            Cornbinder89, what kind of IH rig do you have? I've got a '72 1210.


            • #36
              Two 9670 cabover semi's, one Fleetstar tractor and although not an IHC, a Marmon conventional semi tractor.


              • #37
                Cool man. Thanks for all the help!
                Is there a good resource that you could recommend for learning about auto AC systems and what pressures, etc. should look like?


                • #38
                  Goodheart-Willcox textbooks "Modern refrigeration and Air Conditioning" is a good textbook on the subject.

                  I am not going to recommend a seller, and only mention the text because I found it useful.

                  I use an earlier edition of this textbook, not cheap but covers a lot.
                  The thing to remember about pressures, is they only indicate temp of the refrigerant at the point measured, if the system is properly charged.

                  When a system is properly charged and operating correctly, the low side pressure should indicate evaporation (boiling) temp of the refrigerant in the evaporator, high side should indicate condensing temp in the condenser.
                  A temp vs. pressure chart for R12 and R134a can be found here:

                  High side pressure/temp will be above the temp of the air passing thru the condenser, but you don't want to see it much over 30 deg above the air temp, the lower the better.
                  The low side will be slightly below the air temp exiting the evaporator, so between the frost switch setting (between 30-35 degs) and the outlet (vent temp).
                  I should add that if the engine rpm is driving the compressor at a speed above what is needed, the low side may be lower than the actual evaporating temp, in that case it is the refrigeration control that is limiting the refrigerant and even if the pressure is showing a lower pressure/temp, the refrigerant is all in vapor form after exiting the evaporator.
                  Last edited by Cornbinder89; 06-18-2019, 10:13 PM. Reason: correct temps, 35 not 25


                  • #39
                    Looking thru the new books index, it seams they have dropped automotive A/C in the newer textbook. I would say that it is (or at least my edition) good overview of refrigeration Likely as to due with EPA 608 and 609 certification, where the make a distinction between automotive and general refrigeration.