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New R12 AC system in Dodge D150 blowing relief valve - lack of condenser airflow?

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  • #46
    Well, it might be worth flushing the old one and swapping it back in, just to see if anything changes. I doubt there could be any un noticed restriction before the Tx valve as it would show itself in a marked drop in temp of the line in question. So, that leave after the Tx valve and it hard to check because it is buried. All this assumes you have the ability to save the R-12 and put it back in when the swap is complete.

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    • #47
      A maybe to save most of the R-12? Just heard this is possible. Find an old 30lb. tank and vacuum it out. If metal is kept in dry ice (ask around where to get some) and your engine is fully warmed up with the right set up should get most of it? Measure tare weight of the can you vacuum and again when done see what you got? Only trick I've heard of
      Virtually nobody near me that I know bothers so much as the room for R-12 equipment specific to it anymore or I don't know where they are hiding,
      Tom
      MetroWest, Boston

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      • #48
        I read on the old forum once of an Evaporator that was manufactured wrong, A bunch of the tubes did not flow freon.. IIRCC, they were blocked off on the ends. Drove the guy nuts. He only found it when he cut it apart.

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        • #49
          And I think it would cause the symptoms he is having as well, low flow and the refrigerant will back up in the condenser making it "smaller" and the head pressure will rise, too little surface area in the evaporator would cause real poor vent temps. I hate to stick my neck out and say for sure that is the problem, but it certainly is within the realm of possibility.

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          • #50
            If I were to take this apart again, I would look at EVERYTHING with a skeptical eye. When I had the paint in the condenser issues, the symptoms were similar. (High head pressure, and warm vent temps) Both the evaporator issue and the condenser issue were reported on either this forum and the old one. There were quite likely a bunch of them that hit the market, and who knows where they ended up.

            I am not knowledgable on the inner workings of a TX valve as I haven't had one of them.... But if paint were inside a condenser, would it get caught up it a TX valve? Is there a screen similar to an OT anywhere in a TX system?

            As for bench testing a evaporator... I am thinking that it "MAY" be possible by rigging up a way to run shop air thru them. Run a set air pressure (try to match normal operating pressures) thru both of them and see if you can feel a noticeable difference in how much air exits. It is a crude method, but may tell the truth

            Sadly, just because parts are new.... doesn't mean they are good

            One thing for sure. Running it with the pressures/flow this far out of whack, isn't doing the compressor any good.
            Last edited by huntindog; 07-19-2018, 10:41 PM.

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            • #51
              Quote huntindog ">Sadly, just because parts are new.... doesn't mean they are good<"

              Ha - almost page 5 on this problem that comment speaks volumes!
              Tom
              MetroWest, Boston

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              • #52
                Well, to be fair, it is not the 1st thing I would suspect, a new part, but have been around enough not to rule it out if all other stuff checks out either.
                Dog, most Tx valves have a screen on the inlet, and it could clog, but I believe he has changed it twice. (see above disclaimer). If 20-30% of the tubes (area) of the evaporator are in-op I could see it giving the pressures and temps he is seeing.
                I just wouldn't say it HAS to be the evaporator, but it would be good to rule it out.

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                • #53
                  Originally posted by Tom Greenleaf View Post
                  A maybe to save most of the R-12? Just heard this is possible. Find an old 30lb. tank and vacuum it out. If metal is kept in dry ice (ask around where to get some) and your engine is fully warmed up with the right set up should get most of it? Measure tare weight of the can you vacuum and again when done see what you got? Only trick I've heard of
                  Virtually nobody near me that I know bothers so much as the room for R-12 equipment specific to it anymore or I don't know where they are hiding,
                  I recover refrigerants in this manner.

                  I have some old pure gas canisters from work, about the size of a home fire extinguisher. I changed the fitting to 1/4 flare. I pull vacuum on that, immerse in dry ice/used engine coolant bath, and open the gauge valve. As the refrigerant comes over, it condenses, so there's still vacuum, and it continues.

                  Grocery stores near me sell dry ice. I'm in Arizona, and some shops here still do R-12 too (even "my mechanic" who installed a clutch into my 5-speed 1998 Frontier). He says there's a decent population of older vehicles here/collector cars with AC because we don't have rust.

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                  • #54
                    I picked up a surplus refrigeration compressor for a 'fridge, changed the oil to match the systems I work on, and use it to pump out a system. I think I paid $25 for the compressor and had to braise on some fittings. Depending on how big a vessel you are pumping into, you may need to cool the vessel so the gas condenses.
                    For this type of operation the smaller the displacement of the compressor the better. You want to give the gas a chance to loose its heat and condense.,

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                    • #55
                      I have seen some videos on this type of thing (recovering refrigerant from the system) on YouTube but I have always been unsure about how exactly to piece the stuff together.

                      Also, when you do this, does the refrigerant come in "clean" or does the oil come with it? Can you then turn right around and use it again in the repaired system? I do have an old/empty 30 lb R12 jug but I've read about having to swap out the valve or some such on it and also brazing fittings to it, and I've never done that sort of thing.

                      I keep reading y'alls comments about this damaging the compressor at these pressures and you are exactly right. However, a brand new compressor can be had for "only" $160 or so, and so honestly the compressor being damaged at this point is not exactly a big ticket item that I'm super worried about. I'm mostly just annoyed that it's looking like I'm going to have to do this job all over again from scratch and am very much just leaning towards buying all new parts yet again. I know that's a big jump, but I honestly don't have the time or patience or willingness to keep losing more R12 when for "only" a few hundred more dollars I can just buy yet another new compressor and evaporator etc. and start entirely fresh again.

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                      • #56
                        Bear with me, threads this long get hard to follow. In removing refrigerant generally you are NOT removing oil. As Cornbinder89 said you want it and your hoses, creations all in state of vacuum first then he said and think I did into a cold (cold as you can get) container also if in a state of total vacuum should get most out without oil loss of any consequence.

                        All new parts all over again? NO. Compressor that can pump that high is still compressing it's WHY it's out of range has to be found.
                        Back to maybe page 1 of this. Multiple fans can (not always) fight with each other if in series I think you said OE fan is still in this should really be all it needs if you have a great fan clutch would blow air all over the place up, down and over engine with hood open when bi-metal temp spring is hot enough. If that fan just part works it's in the way. That's why just using water misting (condensers) takes the air flow issues totally out you wouldn't need a fan at all water is many times more effective at heat exchange than air,

                        Tom
                        MetroWest, Boston

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                        • #57
                          Be aware that some 30 lb kegs have a one way valve built in the stem and you can not use them to store refrigerant without cutting the old valve off and putting a new valve on. This was done to prevent people from hooking things up wrong and blowing up the keg. I don't know if it was only for automotive kegs or not. I know I made a tire tank out of an old R22 keg without a problem, but everything I seen in the last 20 years or so had the check valve below the shut off valve in the keg stem, no way to get at it and remove without destroying the valve itself.
                          If I had a clean keg that I knew didn't have a check valve,, I would not hesitate to pull a vacuum on it, pump or use the dry ice method of pulling the refrigerant out of the system, and then re-using the old refrigerant back into the same system. You might loose an oz or two or three in the transfer, but you'll save most of it.
                          Old BBQ propane tanks work well but I would not re used as I don't think there is anyway to be sure all the propane and propane oil is out of the BBQ tank.
                          Any pressure vessel that can take 300- 400 lbs safely can be used.

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                          • #58
                            An old CO2 fire ext would be ideal if the head was adapted to take a valve spud.

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                            • #59
                              Originally posted by Tom Greenleaf View Post
                              Bear with me, threads this long get hard to follow. In removing refrigerant generally you are NOT removing oil. As Cornbinder89 said you want it and your hoses, creations all in state of vacuum first then he said and think I did into a cold (cold as you can get) container also if in a state of total vacuum should get most out without oil loss of any consequence.

                              All new parts all over again? NO. Compressor that can pump that high is still compressing it's WHY it's out of range has to be found.
                              Back to maybe page 1 of this. Multiple fans can (not always) fight with each other if in series I think you said OE fan is still in this should really be all it needs if you have a great fan clutch would blow air all over the place up, down and over engine with hood open when bi-metal temp spring is hot enough. If that fan just part works it's in the way. That's why just using water misting (condensers) takes the air flow issues totally out you wouldn't need a fan at all water is many times more effective at heat exchange than air,
                              If these recovery setups do not remove any oil, why do I always see oil "catch cans" (for lack of a better word) with them? The professional machines I see have this and is actually used as a method by which to determine how much oil to add back to the system?

                              I don't want to come off as argumentative or unreasonable but I assure you the fans are not cancelling each other out or causing an issue here. I have done every practical test imaginable to determine that and my experience on other vehicles as I've said is further evidence of that. With the fans I get much better flow across the front of the truck as evidenced by my "paper towel test" with them vs. the factory fan.

                              Last weekend when I drove the truck after replacing the condenser I spent part of the afternoon with the aftermarket fans disconnected to determine real-world difference with the supplemental fans and/or JUST the factory fan. The only discernible difference was that the compressor cycled OFF at idle a couple of times and then the vent temps went from 60 up towards 70. So I hooked the fans back up even though yes they are a band-aid

                              Of course all this said, I certainly could buy a new heavy duty fan clutch and install it but I really don't feel that airflow across the condenser is the problem - doesn't the fact that the system refuses to cool below 60 degrees on even an extended highway run seem to back this up? Or am I misunderstanding here?

                              I remember all my issues with Civics over the years and their poor condenser airflow - they'd have pretty subpar vent temps at idle, but get them going on the highway it would cool great because you get all that airflow across the condenser. The truck is behaving almost backwards from all my other vehicles I've worked on which all cool much better on highway runs. The truck doesn't.



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                              • #60
                                Just don't compare this to a Civic please with a sideways engine - no comparison.
                                Any equipment to "recover" refrigerant should be separating out anything but good refrigerant to put back later. Super high end ones will just do the whole job punch in what you want it to do and quit telling why it couldn't if so. Mega buck machines none already said here or somewhere for R-12 exist too costly to service and keep for one vehicle a year if that!

                                For a container a used any refrigerant can just momentarily ignore it says don't refill them marked all over them start with anything you use in a full vacuum and lock it there. Learn how to vacuum out your own gauges and hoses too at worst should only have the slightest possible spit of air in moving hoses around and only maybe some lock right at the ends. Too many types of stuff you need to know what you are using not all the rest of every type.

                                The airflow was the top suspect you can just remove the fan clutch carefully and new bolts hold that pulley on. Now no double fanning in front of each other seems strange but may leave radiator and condenser in a slight vacuum spot despite it seems right.

                                Now into "aero-dynamics" only know enough to not do it. Why wouldn't a helicopter use two smaller blades on top of each other? It doesn't' work is why.

                                Remember with air or a vapor it's going from higher pressure to lower pressure limited to density of the air it has available. All that and what has been said is use of water takes all need for airflow OUT of the picture.

                                Eh - this is going to get all drawn out. Did a lot of A/C (not by choice) for yachts! No fans for condensers ever they use heat exchangers like small to larger scuba type things with just the tubes soaked in constant new water the boat is in some small do unreal BTU exchange of heat including cooling exhaust cool enough you can touch it anywhere! That's serious heat exchange!

                                Tom
                                MetroWest, Boston

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