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2001 Durango not cooling pressure seems ok

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  • 2001 Durango not cooling pressure seems ok

    Working on a 2001 Durango and I think the condensor or receiver-dryer is clogged but dont want to just part change. With the ambient temp about 90 f at idle low is 55# and high is 200# at ~2000 rpm the low is 35 and the hi is 250#. the front and rear discharge air is about 80 f. The pressures quickly fluctuate with rpm change and are stable at speed. Since this truck has two expansion valves I doubt both are bad. Compressor was changed sometime in history. a/c line under hood does get cool with some condensate but at 90f I would expect more. Charge is about 40 oz or 2.4 pounds. Can anyone confirm or deny my opine to replace the condenser and receiver?

  • #2
    Low side pressure is relative to evaporator temperature. 35 PSI at 2000 RPM seems pretty good. And your high side looks good for that ambient temperature. I would feel the evaporator case inside the truck right under where the evaporator is and see if the plastic housing feels cold. I wonder if you have some sort of temperature blend door issue?

    Strange though that front and rear are acting the same way. Unless there are two problems, i.e., maybe blend door in the front, and bad expansion valve in the rear. If it were me, I would start with the focus on the front only.

    I have also seen this before on systems that were over-oiled. It's often the case when multiple recharges or top-offs are done with small cans that feature oil and other leak sealer additives. Each time the user adds refrigerant, they inadvertently get a little extra oil charge which just gets worse with every top-off to the system. Pressure will seems good, but the system will be logged with oil. That's always fun to try to figure out.

    P.S. Receiver restrictions and condenser restrictions can often be felt as temperature anomalies. I have even seen a condenser cold and sweating in a corner which really made the decision to change it pretty easy. Expect to normally see very little temperature difference between inlet and outlet of a receiver and about 40 degrees difference between inlet and outlet of a condenser.
    Last edited by CJB; 08-30-2020, 04:51 PM. Reason: Had to edit because i failed to read that both front and rear were blowing warm.


    • #3
      250 psi is 147 deg condensing temp or almost 60 deg over ambient! See how hot the outlet of the condenser is compared to the inlet. How good is the air flow over the condenser? ANY corrosion on the condenser tubes reducing heat transfer?
      Excessive oil can reduce heat transfer but isn't the 1st thing I would suspect. Overcharge can reduce the "effective" condenser size, resulting in high condensing temps/pressures.
      You could try misting the condenser with water at 2000 rom and see what the pressures do. Without knowing the dew point I can't say anything about seeing condensate on the suction line.


      • #4
        Thank you CJB I will temp scan it better and see what the condenser and tubes are doing. I suspect I am on the correct path. Also the discharge temps didnt change at any rpm. blend door working for front for sure rear did not change when I went from cool to heat, perhaps was not patient enough. The case is not cool. Temp drop from top to bottom of the condenser is about 20d f Lo side tubing at the valve is 140d f on the low side and 165 d f on the high side.temps are slightly higher at the condenser.


        • #5
          O.K., first, I'll always have to agree with Cornbinder89... I was reading 35/200 PSI and I didn't think that was too bad. Actually though, I wouldn't think 250 PSI would be problem enough to cause 80 degree vent temperature. Yes, if 250 PSI was responsible for a 60 PSI low side, but with a 35 PSI low side I would still expect some decent vent temperature. Now something simple that could be done is to reduce the charge to the single unit specification, which I think is 1.7 LB of R134a. See what impact that has on vent temperature. I like the idea of misting the condenser with water as this should very effectively bring down the high side pressure.

          P.S. Off to get some better reading glasses...


          • #6
            74d f dew, 90 d f ambient 1500 rpm discharge temp 70 d f . 189 vs 192 d f at the expansion valve. 136d f at the top of condenser 105 at the bottom of the condenser misted. l pressure 38psi hi pressure190psi


            • #7
              Reducing the charge did nothing until empty. Tried that first. The complete system is externally clean with no obstruction or contamination.
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              • #8
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                • #9
                  condenser temps at the same time
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                  • #10
                    When everything looks good and it still won't work Every year I get a few like this...

                    This may be stupid to ask, but have you tried it with the hood shut? Here's the long explanation for the reason I ask... I had a Ford E-series van a few weeks ago that really had me stumped. I mean like all day stumped. It was a mobile dog grooming van. Pressures and charge level was verified by me and and all new parts were installed by the another shop that couldn't get it to cool properly. I fist noticed the evaporator was loose and moving around so I surmised that some un-conditioned air was flowing around the evaporator core and not through it. Thus resulting in lousy vent temperatures. I pulled the evaporator, resealed it with Armaflex tape, vacuumed and recharged the system only to find the same lousy vent temps. I double checked everything except the fresh air door. The previous shop had unplugged the vacuum line going to the max air door because the evaporator was prone to clogging with pet hair. My under-hood temperatures were hi and that air was being brought in from the fresh air cowl and making for some really bad vent temperatures. After finding this disabled max air door I closed the hood and vent temps dropped 20 degrees, which gave me about a forty degree split. So, I had to ask.

                    Your pictures are great, and definitely a help. I still feel like 35 PSI low side should really produce some cold air somewhere. If the back was cold and front wasn't, I would blame the front expansion valve. If the front was cold and the back wasn't I would blame the rear expansion valve. When you have two expansion valves, pressure problems can be masked by the properly working valve. Problem is, you have good pressures but poor vent temps at both locations. Like you actually have two different problems.

                    Have you tried pinching the heater hoses off?

                    Could the system have a gross overcharge of oil?

                    Did this problem happen at all at once or did this problem only develop after some initial repair. I mean has the system ever worked?


                    • #11
                      I was gifted this vehicle for unrelated repair and " oh by the way" ensued. I noted that the compressor appears to have been changed at one point but this new owner knows nothing of its history. Its looking like I will offer them a flush and replace the receiver drier. The oil issue sounds very relevant but wont know until I purge the system. In my opine as you suggest it is acting as over charged (too much oil) or an unknown obstruction but I find no obvious spots of temp variation. I am not in the business but am a relatively skilled and experience hobbyist but not expert, guess will never be. If I find the answer I will surely post, many do not. Thank you!!!


                      • #12
                        Misting shows when you get the heat out the pressures drop to more where I'd expect them to be.
                        My be it is just the picture but the condenser seams damaged on the right side. If you can't get the heat out at the condenser, it just keeps recirculating.
                        you wrote this "189 vs 192 d f at the expansion valve" Are you really saying the refrigerant tube is 192 deg F at the expansion valve? either your IR thermometer is off or I am mis understanding what you are saying there.
                        With dew points in the mid 70's and temps in the 90's the system is going to struggle. It takes a lot of BTU's just to wring the moisture out of the air.
                        Did you notice when you misted the condenser, the temp at the inlet also decreased? It is showing that without misting you are re circulating a lot of heat.
                        I'd concentrate on the condenser end of things. Both the high and low side dropped to where I would expect them to be when you misted. SO look at air flow across the condenser, look at the condenser real carefully. I can show you a condenser that looks good from casual look, but if you take a magnifying glass and look close at the fin/tube bond, you'll see white corrosion preventing the heat from conducting from the tubes to the fins.
                        It is my experience, OEM's make the condenser just big enough if everything is prefect, any degradation and it can't keep up. With dual air, I would consider replacing with a high capacity "generic" condenser if a bigger one can easly be fitted.
                        Not only will an oversize condenser remove the condenser as the limiting factor in the a/c system, it will lower the pressures.


                        • #13
                          Oh, and I don't think you have an obstruction, with those, the high side goes high and stays but the low side goes really low, often below atmospheric (vaccum) because no or almost no refrigerant is able to make it back to the suction side.


                          • #14
                            One more thing to keep in mind, You will not see vent temps drop right away. It takes my trucks almost 30 mins to reach the vent temps you'd expect to see via the pressures. On the Trucks, the evaporator is under the passenger seat, the ducts run under a "false floor" up and across the dash. It takes a long time to cool all that duct work, Once it get cool, it stays that way for the rest of the day.