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A/C on a 95 Cavalier

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  • #442793
    BubbaTeaBubbaTea
    Participant

      Replaced compressor and added 1.5 lbs of charge. Gauges read 27 and 150H.

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    • #442794
      college mancollege man
      Moderator

        how did you weigh in 1.5 lbs of charge? when you put the new compressor in did you pull out the metering tube and inspect/replace it?
        also did you get a new accumulator drier? before you added charge you should have pressurized the system with nitrogen and let it sit
        for 24 hrs to be sure that the pressure did not drop.this way you don’t waste refrigerant. as for the dye. did you use uv dye or just the red?
        you might see it but on a 70 f day the humidity is low so condensate may not be produced. your pressures don’t seem that far off from the
        manuals spec. with the fan on high and set to max cool. you air discharge out of your vents should be between 35- 40 f +or –
        check to see if your cooling fans are on. also check for debri blocking the condenser/ radiator. keep us posted. C8-)

        I also forgot to ask if you used a vacuum pump to remove air and moisture from the system?

        #442795
        BubbaTeaBubbaTea
        Participant

          OK, I wanted to spare everyone a long drawn out story:

          I replaced the compressor (v5), Accumulator, a hard line from the evaporator to the accumulator (old PS hose wore it out which burst), low side schrader valve, O-ring to the 0rifice tube connection and 0rifice tube, o-ring to the inlet of the condensor. None of those connections are leaking, btw.

          Evacuated system with vacuum pump for 45 minutes and let rest for 30. Held vacuum. The service manual states that no compressed air should be used on the system.

          Added two 12oz. cans (1.5lbs) of Johnson R134a that I got from Big! Lots and charged system with a short charging hose. Worked great! Then …see above.

          Looked in my service manual and it says add 14oz of refrigerant based upon pressures given. All the 14oz cans in my area have snake oil added to them and no UV dye so I added a 12oz can of R134a with a UV dye – the bright yellow stuff. My LED flashlights light that stuff up big time and I have a black light too.

          Nothing. No leaks, no creaks, no streaks. The condenser is nice and clear.

          Temp test of accumulator and 0rifice tube:
          Both are nice and cold. The condensate is coming out nice and clear.

          It’s warmer today (80 degrees F) and I put the gauges on. It starts out at 35psi and 165psi and then drops to 27psi and 155 psi Low and High respectively.

          Here’s a question. If nothing shows up and it holds its charge, would there be an issue to run the system slightly under charged? The pressure sensor is there to make sure there’s enough refrigerant to keep the compressor healthy.

          Also, this is the third time I put the gauges on. Aren’t I adding air to the system whenever I do that? I just read about zero-loss hoses; which I should have.

          #442796
          MattMatt
          Participant

            The amount of air you are adding is tiny. Have you put the thermometer in the vent yet? Like college man said, yer pressures are pretty close. It hasn’t really been hot at least here in Ohio. When the temp goes up, so will your pressures.

            #442797
            BubbaTeaBubbaTea
            Participant

              Quoted From Beefy:

              The amount of air you are adding is tiny. Have you put the thermometer in the vent yet? Like college man said, yer pressures are pretty close. It hasn’t really been hot at least here in Ohio. When the temp goes up, so will your pressures.

              Oops, I forgot to post that: 39 degrees F at the vents.

              From what I’m reading (Birch), zero-loss hoses; which should come with all R134a manifolds (right?) and unless I’m really misunderstanding something, would mean I wouldn’t have to worry about air getting into the system.

              I’m just really paranoid, I guess. I read this stuff and they’re are all these warnings about no over charging, under charging, etc ……

              Oh, and what I also forgot to mention that I did add PAG 150 105ml to the accumulator and another 62ml to the compressor – according to manual in addition to another 29ml later with a charge. There was a previous leak that I missed the first time around and wanted to replace that oil.

              #442798
              college mancollege man
              Moderator

                ok sounds good so far.you added 2 twelve ounce cans 134-a to get 1.5 lbs total system charge. the part that throws me is you added 12 oz
                with dye. was this in addition to the 2 twelve oz cans. or was one can with dye and the other with out totaling 24 oz total just need to clarify.

                #442799
                BubbaTeaBubbaTea
                Participant

                  Quoted From college man:

                  ok sounds good so far.you added 2 twelve ounce cans 134-a to get 1.5 lbs total system charge. the part that throws me is you added 12 oz
                  with dye. was this in addition to the 2 twelve oz cans. or was one can with dye and the other with out totaling 24 oz total just need to clarify.

                  Answer to questoin: Two 12oz cans with no UV dye and then an additional 12oz can with UV dye.

                  The long story

                  After repairs, I charged the system with two 12oz cans of the cheap stuff.

                  Then, after the system would sporadically work and after putting the gauges on and consulting the manual (static pressure was 47-48 psi needs to be 50psi+), I added an additional 12oz can with UV dye – according to the manual it says 14oz.

                  Static pressure is now: LOW 58psi and HIGH 58psi. So far, so good.

                  Here’s the weird part, after adding that last 12oz can, my gauges didn’t change during operation. Before and after that last 12oz can, my gauges were (after running a few minutes): LOW 27psi; HIGH 150psi.

                  That’s right, adding that last can of 134 didn’t do anything for the operating pressures; just the static pressure.

                  In nutshell:

                  Charged system with two cans (1.5 lbs).
                  After running great for a couple of weeks, system then didn’t run all the time.
                  Added one more 12oz can with UV dye.
                  Static pressure is where it should be. Operating pressures didn’t change.

                  #442800
                  college mancollege man
                  Moderator

                    well you did good up until you stuck in that 3rd 12oz can. the system is over charged. you can’t go by static charge.once the charge was weighed
                    in. 24oz thats it done. the pressures are going to vary according to load. C8-)you may have a problem with the low pressure switch. unplug
                    the connector and plug it back in. also inspect the connector and the switch.

                    #442801
                    BubbaTeaBubbaTea
                    Participant

                      So, my original problem – after the first two cans – of it working sporadically, could have been really been a bad low pressure switch?

                      By “working sporadically” I mean that sometimes the A/C would come on and other times it wouldn’t – all within the same trip.

                      To clarify, when the problem started, I did put the gauges on and saw that the pressures were low. Then I added the extra can to bring the static pressure up over the 50 psi threshold and to find the leak with the UV dye – which I’m still not seeing.

                      It’s a thought though. I’ll test the switch tomorrow.

                      #442802
                      EricTheCarGuy 1EricTheCarGuy
                      Keymaster

                        First AC work is something that I recommend the DIY avoid because of situations just like this there is so much you need to know in order to properly service an AC system, in fact I know many professional techs that won’t touch it because of their lack of experience with it. That said your high pressure is way too low it should be almost twice that at around 250-300psi, you may have an issue with the expansion valve or orifice tube (not sure what that system uses) but it’s the device that regulates flow into the evaporator. This is where it gets interesting because if that is the case you’re going to have to take the vehicle to a place to have what you’ve already put in the system removed so that you can open the system again to replace the expansion valve and THEN evacuate and recharge the system, afterward recheck your pressures and vent temps.

                        #442803
                        BubbaTeaBubbaTea
                        Participant

                          My system uses an 0rifice tube. (Use a zero ‘0’ instead of an ‘o’ to keep the site software from censoring the name – if someone is offended by ‘0rifice’; they need to get a grip )

                          I have been running the system and following the diagnostic charts in the service manual – the GM service manual. And the system shows no signs of a problem with the 0rifice tube. I have found one problem so far and fixed that and the system is stabilized. I’m shopping for a guy to evac it and recharge. I’m real curious to see how much is left in the system.

                          Which is funny, that problem I found, was a torque problem – a torque spec that for the life of me I can’t find in the manual.

                          That schrader valve I put in? Wasn’t tightened enough. Tightened it some more and the leak stopped.

                          #442804
                          MattMatt
                          Participant

                            At this point, I’m not even sure what your question is. I dug out my textbook from my HVAC class, and your pressures are not abnormal for that system. You say you are getting 39 degrees at the vents. What more can you ask for? It sounds like you found one terrible shop regarding your parking brake, and you are just here to bust the industry’s balls. What is actually wrong with your car? Is the system not running? I’m confused. It your pressure is at the specs and not running, then yes, look the the low or high pressure switch. Every system is extremely different. Some stop the compressor based on low pressure, some based on high pressure, some do both. Is the A/C still pumping out 39 degree air at the vent?

                            #442805
                            BubbaTeaBubbaTea
                            Participant

                              I figured it out. Thanks for the input.

                              And I apologize for offending anyone or any industry.

                              #442806
                              BubbaTeaBubbaTea
                              Participant

                                It was really under charged and I had a leaking schrader valve that I fixed by tightening some more. My vent temp is now 29 – 30 dgrees F.

                                #442807
                                MattMatt
                                Participant

                                  Nice job man. Congrats on the fix.

                                  #442808
                                  EricTheCarGuy 1EricTheCarGuy
                                  Keymaster

                                    Schrader valves are probably the #1 source of AC leaks from what I’ve seen so I’m not surprised by that at all, glad you found it.

                                    I’ll look into the censoring issue but thanks for keeping us up to date and posting the fix.

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