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Front vs. Rear window switch ('85 Cabrio)

Discussion in 'Mondial' started by Albert Penello, Mar 15, 2020.

  1. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
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    #1 Albert Penello, Mar 15, 2020
    Last edited: Mar 15, 2020
    Question about window switches for my '85 Cabrio.

    The parts manual lists two different switches for the Front and Rear windows. Looking at them, they are physically the same except the front window switch has all 5 pins, and the rear window switch only has 4 pins although they have the same connector.

    I'm curious if the 5 pin ones will work in the rear, since they are more readily available both new and as reproductions.

    Why do the rear units only use 4 of the pins?

    Thanks!
     
  2. Steve Magnusson

    Steve Magnusson F1 World Champ
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    I think, electrically, you can use the 5-pin switch at the rear if you add a wire to connect terminal 2 to terminal 4 like in the harness for the front switches (on the 4-pin rear switches this same connection is built inside the switch itself and terminal 4 is eliminated). You can compare the internals of the 5-pin front switches (88 and 94) shown in Fig 6 of the 1984 US Mondial QV wiring diagram book to the internals of the 4-pin rear switches (188 and 189) shown in Fig 7.

    PS They mangled the description of 94 for Fig 6 -- it is a switch, not a motor.

    My guess would be that these 5-pin switches were from another make of car, more like a 308, where the driver has two switches (one for the LH window and one for the RH window) and the passenger has a single switch for the LH window -- this arrangement requires a more complicated wiring interconnection network. As I mentioned, you can see on Fig 6 that the wire in the harness for the front switches connecting terminal 2 to terminal 4 effectively changes the 5-pin switch into a 4-pin switch.

    PPS The graphics on the two rear window switches must be different as the SPC shows the LH and RH rear switches have different part numbers.
     
  3. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
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    Steve you are a lifesaver.

    Yes they are different switches with the the correct window "side" but this is sort of irrelevant to me at this point since the old paint is practically wiped off. Looks like they are jumpering the two pins to ground to I think I can take care of that on the harness side pretty easily. I'll order a set of repro switches and report back.
     
  4. moysiuan

    moysiuan Formula 3
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    The rear 4 pin ones are available, without the window icons. They cross to the BMW 5 series of the period.
     
  5. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
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    Really? I know the mirror switches cross over but I've never seen a window switch like that on a BMW? I have 6 series of that era (an 86 e24 which is same as the e28 5 series) and BMW's use a two-button switch. If you have a PN please share thank you!!
     
  6. moysiuan

    moysiuan Formula 3
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    Albert Penello likes this.
  7. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
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    #7 Albert Penello, Apr 4, 2020 at 1:02 PM
    Last edited: Apr 4, 2020 at 1:13 PM
    Ok for anyone interested - you can pretty easily adapt the 5pin switch to the 4 pin switch harness/plug. It's the exact same connector, and the only difference is the internal grounding of the 2nd and 4th pins so the factory harness is missing a ground wire (there is an empty hole). It's very easy to de-pin the single ground wire from the connector, create a "bridge" wire between Pin 2 and 4, and then connect to the factory ground harness. Takes all of 5 min.

    It does require you to get set of male/female .187 spade connectors which are a little smaller than the standard ones you can get at the parts store.

    The benefits to do this are pretty great.

    1. Doesn't mess with the factory wiring - no cutting or splicing.
    2. Allows the use of much cheaper aftermarket switches or the much more available factory front switches
    3. You can put either the 4 or 5 pin switch in after this mod without redoing the wiring.

    The only downside is you don't get the little window Icon, which in my case had rubbed off anyway.

    Since I wasn't sure if this was going to work I got a set of 4 switches off ebay $16.00 shipped. They actually seem pretty well made, too. Did up some quick connections, plugged them in and rear windows are working great.
     

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