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Cant get compressor to engage

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  • Cant get compressor to engage

    Ive been trying to get my compressor on my Bmw 750il 1992 running I found a leak coming from the ac line going from the compressor to the evaporator. I noticed that it looks like someone filed the side of the ac line where the line connects up against the compressor I'm guessing this is why its leaking because this is where the leak is coming from. Here a picture of the filed area I circled it in red https://imgur.com/khSe1cG . Does anyone else think this could be the reason my compressor wont engage.

  • #2
    If it is low on refrigerant it will not engage, safeties will prevent the compressor from running when low. Fix the leak, recharge and go from there.

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    • #3
      Before you take it apart, add some UV dye Freon, run it a few minutes, then check with a UV light.

      You didn't give any additional information about the car, such as when the AC last worked, but a car that old would most likely need a new evaporator if it hasn't already been replaced.

      10 - 14 years is the lifespan of evaporators, then they corrode through from debris in the evap housing. I added air intake filters to my older vehicle to prevent debris from entering the housing. Hoping this will extend the life of the evap core.

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      • #4
        The car was retrofitted from r-12 to 134-a in 2000, that's the last time I know it was worked on. The compressor wasn't working so we filled it with refrigerant a few months ago and got the compressor to run but it wasn't very cold air coming out of the vents and then I realized the leak at the compressor so I dissembled the ac lines to the compressor and the ac lines going to the condenser then I flushed the condenser and the ac lines going to it. Then I replaced the drier and o-rings that I had access to, drained and refilled compressor oil. Then pulled a vacuum on the system for 2 hours then filled it with refrigerant and the compressor couldn't engage and it keep leaking from the compressor that's when I realized the crack the the bottom line. Currently I'm waiting on a AC line to see if that fixes the leak by the compressor.

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        • #5
          So I installed the new pipe pulled a vacuum for 2 hours then started to fill the system with refrigerant and I saw the compressor engage for about 5 seconds then turned off so I took the relay out and bypassed it with a wire so the compressor was running right when I started the car so I started filling the system with the rest of the bottle of refrigerant and took most the bottle then the belt started slipping on the compressor and made a loud screeching noise and then the compressor clutch shut off so I turned off the car. I then pulled the wire out and put the relay back in the car and tried the running the compressor it tried turning on but the belt kept slipping for about 3 seconds and then it gave up and just wouldn't engage. What could my issue be so far I haven't see anymore leaks from where it was leaking from.

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          • #6
            Did you measure the oil when you put it in? Compressor can be hydo-locked if too much oil is in it. By "bottle" do you mean 12 oz can or something else? Do you know the capacity for the oil and refrigerant by weight? What pressures are you seeing on the gauges?

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            • #7
              ok I've determined that my compressor has internally failed in some way because it wont even accept a 12oz bottle of refrigerant it could only take 10oz out of the 12 and the gauges are rising together when I fill the refrigerant in the system. readings on the low side were 46 psi and readings on the highside was 45 psi with only about 5 oz of refrigerant in the system at that time when I put the rest of the 5 oz that I could get in the system the lowside was reading 83psi and the highside was reading 85 psi. since the readings of psi are so equal to each other when the system being filled I believe I have a bad compressor.

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              • #8
                Only if those pressures are with the compressor turning, the high side valve closed, and the low side open.

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                • #9
                  I got a new compressor, expansion valve, and drier the car was retrofitted in 2000 from r-12 with mineral oil to r-134a with ester oil. I'm doing a full system flush and replacing everything except for the condenser and evaporator my question is should I use ester oil since that's what they used when they retrofitted it or should I use pag oil.

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                  • #10
                    Ester can handle some Mineral oil and R12 in the system which is why it is used in retrofits. PAG is preferred for a clean system being run on 134a. If your old compressor came apart I would consider replacing the condenser also.

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                    • #11
                      my condenser is a old style condenser so it can be flushed easily I plan on using the same condenser. It looks like pag oil is my best option here since Im completely flushing the system out so I will be using pag 46 will report back when system is install and filled with refrigerant.

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