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  1. #1
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    Member No: 64099 tspot100 is an unknown quantity at this point tspot100's Avatar
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    Headlight Switch Gremlin

    Anyone know why the rheostat in the headlite switch on my 72 Bav will
    glow red perodically? Is it a short somewhere? The instrument lights do not work either. The #2 fuse will blow if I pull the switch out and turn it all the way to the right(brighter I imagine). I noticed a funny burning smell and chased it down to the switch.Any ideas?
    Oh yea, anyone have an extra headlight switch they would like to part
    with?
    B
    72 Bav
    74 Bav


  2. #2
    Dave Beddows
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    Re: Headlight Switch Gremlin

    The dimmer circuit off the headlight switch is a blue/white or blue/grey colour code. (I think blue/grey. Blue/White is BMW 507)

    You will find it makes an appearance in the following locations:
    -Bulbs on back of instrument cluster (I believe 4 of them)
    -2 Bulbs on the clock
    -2 Bulbs in the heater controls (1973 -)
    -1 bulb in the steering column by the key
    -And in some cases a lead may be run down to the radio for use with stereo's with dimming circuits on their back lights.
    - If your car is an automatic it may appear by the shifter but I don't believe they did this on the Bav's. it was quite common for the later model BMW's.

    Have I missed any?



    I Have seen many cooked headlight switches. It is possible the switch is broken internally and is shorting out, however, I would be inclined to believe the problem is at one of the bulbs. You can tell by getting an inline fuse (try 2A) and bridging it between the red (hot wire) on the switch and the blue/grey wire. If it blows instead of all the lights working then you have to do some chasing.

    Start with the bulb by the key. It is easy to get to. 4 bolts hold the underside cover. It is common to see the wire for this bulb trapped in the underside cover causing a short.

    The next easiest bulbs to check are the clock (if you have small double joined fingers)
    Then the instrument cluster (Take access through the speaker grill)
    Then the heater control. (Careful the mounting studs are easily broken.)


    Have fun, keep us posted.

  3. #3
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    Re: Headlight Switch Gremlin

    Dave,
    Thanks for the info. I dug out my trusty "big blue binder of knowledge" for schematics and went at it. I also got a short circuit finder from Mac tools. Handy little gadget.
    The problem was just where you said it may be. So simple! One of the wires from the a clock bulb was grounding on the clock housing. Very frustrating I must say. I had the cluster out, all the fascia trim etc...
    Thanks again for the info. Another kind soul helped me out with a good used switch so now the 72 is happy.(for now...)
    Baron 72 Bav
    74 Bav

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