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  • AC Compressor diode

    I recently changed out my Ac compressor and in taking out the old one, there was a diode wired in line with the one wire coming out of the compressor. When the new compressor was put in place, the diode was not put back in. Is it necessary and if so, what does it do? There was no BMW part number on it, so that makes me think it was done after the fact previously.

  • #2
    Originally posted by strube View Post
    I recently changed out my Ac compressor and in taking out the old one, there was a diode wired in line with the one wire coming out of the compressor. When the new compressor was put in place, the diode was not put back in. Is it necessary and if so, what does it do? There was no BMW part number on it, so that makes me think it was done after the fact previously.
    Those diodes were installed at the factory and are necessary for operation. Your new compressor may be different and not require it, but I tend to think that it would. Is your new compressor operating properly without the diode in place?
    Eric Giles
    '07 X5 4.8i
    '01 325i
    sigpic

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    • #3
      My compressor was changed prior to me buying the car. I replaced it with a unit that look exactly the same. They do seem to be factory compressors that were rebuilt after looking at pics of compressors for sale on here. The AC still works and blows cold without the diode. My compressor currently has a single wire that comes out of it that is connected to another single wire. I have seen some that have a connector with three connections and a diode, so mine is definately different, I just don't know if that will be a problem.

      Any chance you could take a picture of how yours is connected to do a comparison?

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      • #4
        This is from BMW “Whenever the Compressor Clutch is de-energized, the collapsing magnetic field induces a voltage in the winding. The Clutch Diode provides a path for the resulting current.”


        Originally posted by drinaldis
        I dated a girl who used to do the reverse grind. I kinda liked it.

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        • #5
          Strube,

          Sorry to hijack this thread but I want to ask you a question about your old setup.

          I was trying to get my ac working yesterday while following the schematic from the ETM.

          Basically there is only one wire that comes off the compressor. This is from the diode. Based on the diagram it looks like that black wire from the diode connects to slot 3 in the c110 connection. Then there is a black and red wire that loops from 3 to connection 2. Then a wire from 1 goes back up to the left side of the engine bay.

          Does this sound right? I want to get these wires propelry connected before charging the system.

          Sorry again, for the hijack, but it sounds like your familiar with the same setup as I have now.


          Thanks,
          Joey
          http://JoeysM3.com

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          • #6
            Originally posted by e30m3power View Post
            Strube,
            Basically there is only one wire that comes off the compressor. This is from the diode. Based on the diagram it looks like that black wire from the diode connects to slot 3 in the c110 connection. Then there is a black and red wire that loops from 3 to connection 2. Then a wire from 1 goes back up to the left side of the engine bay.

            Thats exactly how my car is set up and it's always worked.


            Originally posted by drinaldis
            I dated a girl who used to do the reverse grind. I kinda liked it.

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            • #7
              OK great,

              Thanks Jeremiah.
              Seems so weird to me the way that's it's hooked up.
              http://JoeysM3.com

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              • #8
                Originally posted by Jeremiah View Post
                This is from BMW “Whenever the Compressor Clutch is de-energized, the collapsing magnetic field induces a voltage in the winding. The Clutch Diode provides a path for the resulting current.”
                So without the diode, what would this do to the system?

                To the other posters, my system is different than what you are explaining. I just have the wire coming off the compressor (no diode) and it connects to the wire that goes off into the harness behind the headlight. There is no other connection.

                I used to have the three connector thing, but it has been changed. Could you post a pic of what you are talking about, I would love to see. I never understood why the looped wire was there though. I never had anything connect to it, so it just looped back into nothing. Sort seemed wierd.

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                • #9
                  Originally posted by strube View Post
                  So without the diode, what would this do to the system?

                  To the other posters, my system is different than what you are explaining. I just have the wire coming off the compressor (no diode) and it connects to the wire that goes off into the harness behind the headlight. There is no other connection.

                  I used to have the three connector thing, but it has been changed. Could you post a pic of what you are talking about, I would love to see. I never understood why the looped wire was there though. I never had anything connect to it, so it just looped back into nothing. Sort seemed wierd.
                  You probably have the diode; it’s on the compressor wiring side. W/o the diode the compressor will burn up the evaporator temperature regulator over time.


                  Originally posted by drinaldis
                  I dated a girl who used to do the reverse grind. I kinda liked it.

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                  • #10
                    I have it, but its not connected and is in a baggy on the floor board I will go ahead and splice it back in to avoid any potential issues.

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                    • #11
                      Yes very important the Diode prevents from AC coming back and damaging the circuits.
                      Fully Restored 1985 Corolla GT-S
                      1987 328ci SR20DET Drift Car (Will Convert to M3 Spec soon)
                      1989 Honda Civic Si-R Current Project
                      2002 Corolla CE Daily Driver

                      www.TheTunerSource.com

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                      • #12
                        I tried to find the AC compressor wiring picture on Realoem.com and can't.

                        I found the pic of the compressor but it doesn't have the how the diode wire connects to the c110 connector in there. Is this the wrong place to look?

                        I want to order a new c110 connector with the connections and need the part #.
                        http://JoeysM3.com

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                        • #13
                          I couldn't find it on there either. You can use the same plug housing that is used for the fan switch. The part number is 61131378410. It looks just like the three connector holding thing for the AC, but doesn't have the handles.

                          61130007444 is the male wire connector that is on the other end of the diode. And 61130007442 is the female end. This is the one that loops on itself in the plug housing.

                          You can find each of these in "vehicle electrical system" under diverse plugs and connectors.

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                          • #14
                            Nice,

                            Thanks Strube!!
                            http://JoeysM3.com

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                            • #15
                              For those that wonder, I've used the Polar Bear Inc. compressor and it seems to be working for now. At 215, its a much cheaper solution than going through the dealer. I figure I can go through 4 of these and still come out ahead.

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