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A/C Woes - What should I tell the HVAC guy?

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    A/C Woes - What should I tell the HVAC guy?

    Hey guys,

    Recently I took my 325E in to get the AC fixed. I purchased several cans of R12 coolant from a local seller who had a couple boxes left over. The AC guys (quite reputable apparently) agreed to use these cans to put in my car. They pulled a vacuum on the system. I was chatting with the individual who was doing this, and I asked if it was holding the vacuum. He said "let's see", and turned off the machine for no more than 10 seconds. The gauge didn't move.

    From what I'm reading, it seems normal to hold the vacuum for much longer than that amount of time to check if the whole system is actually tight. So, I noticed that the AC did not get cool at all today. I checked the sight glass on the AC dryer and noticed that there were bubbles in there. I called up the place and I asked them if this was normal and they suggested I bring it down. They called me a few hours later, they said they were unable to find any leaks with their electronic leak detector and they could not find any of the UV dye on any of the components within their sight. The gentleman working on the car said that the compressor was only pushing out 10 psi of pressure (I may be a bit fuzzy on these details). I asked him 'Does that mean it's lost coolant?' and he said yes. He stated that the system had simply been topped off and that I was good to go. They did not charge me for anything. Sure enough the AC works again, but I am still seeing a little bit of bubbles in the site glass on the dryer.

    I am at a loss because as far as I know they did not fix the actual issue. To me it is as if they simply applied a 'Band-Aid' and this same issue will come up in a week. Basically, I'm leaking expensive R12 into the air. They did state the first time around that they guarantee their work for '90 days'.

    My understanding of air-conditioning is limited, but my assumption is that if it is leaking now, then simply topping off the system is not going to fix this. Any ideas on how I should communicate this to them? Am I just an idiot and I'm assuming the wrong things?

    tl;dr Took the AC system to be charged with R12. A week later it does not work. They told me it has lost pressure. They checked for the UV dye and with an electronic tester, could not find anything so they topped it off and sent me on my way. This is going to continue to leak I assume. I want to know how to get them to look into the issue further without coming off as an idiot.
    Last edited by Timp; 07-25-2012, 10:56 PM.
    Newb to all the things.

    #2
    usually you should hold vac for like 30 mins.

    topping off will not cure the problem as you will have condensation get into the system, and it won't perform well. You need to vac the system, put in some dye and figure out where the leak is. Until you do that you're going to be wasting your money and hurting the environment.

    Also, when charging you should be at like 2.5k so that the compressor is working as if you are cruising down the road. Once the car is charged to the correct amount and leak free, you should be good to go. When you're putting freon in the system the compressor should suck it down fairly quickly. If it isn't the compressor might have issues. They should notice this if they were charging it, though.
    '84 318i M10B18 147- Safari Beige
    NA: 93whp/90ftlbs, MS2E w/ LC, 2-Step
    Turbo: 221whp/214ftlbs, MS3x flex @ 17psi

    Comment


      #3
      A leak check firstly should NEVER involve the use of UV dye, as it is a contaminant. Secondly there are different types of leaks- high pressure leaks and low pressure leaks. The system should be tested with varied pressures of dry nitrogen and squirted with liquid external leak detector to properly locate leaks.

      Also in order to determine the presence of moisture in the system (which could be causing your suction pressure and bubbling problems) the system should be evacuated using a micron gauge which will tell the technician the degree of vacuum that has been achieved. Auto shops rarely manage to execute any of the aformentioned.

      Comment


        #4
        Originally posted by Ryann View Post
        A leak check firstly should NEVER involve the use of UV dye, as it is a contaminant. Secondly there are different types of leaks- high pressure leaks and low pressure leaks. The system should be tested with varied pressures of dry nitrogen and squirted with liquid external leak detector to properly locate leaks.

        Also in order to determine the presence of moisture in the system (which could be causing your suction pressure and bubbling problems) the system should be evacuated using a micron gauge which will tell the technician the degree of vacuum that has been achieved. Auto shops rarely manage to execute any of the aformentioned.
        this guy seems to know more than me, and I would listen to him. I've only had some experience around my father who has been doing HVAC work for a while.
        '84 318i M10B18 147- Safari Beige
        NA: 93whp/90ftlbs, MS2E w/ LC, 2-Step
        Turbo: 221whp/214ftlbs, MS3x flex @ 17psi

        Comment


          #5
          Thanks for the suggestion guys. I went ahead and called them, and they said that this is an ongoing process and due to the fact that they were unable to find any leaks the next time this happens they will just need to look into it again and hopefully catch the week.

          To make it easy on them I'm going to dig into the center console so that the expansion valve and the other fittings are available. I found some constructions for this here:

          Newb to all the things.

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