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456 H/L motor

Discussion in 'Technical Q&A' started by cptn.Big, Nov 8, 2024.

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  1. cptn.Big

    cptn.Big Rookie

    Nov 17, 2008
    17
    #1 cptn.Big, Nov 8, 2024
    Does anyone know the wiring/pin descriptions for testing a H/L motor? I've got one light that pops up and down perfectly and the other that doesn't. I have removed the 'bad' one and tested it plugged into the wiring harness of the 'good' one and still nothing, so its the motor unit and not a chassis wiring issue. It does 'try' to work, IE; there is some movement under power when manually rotated and activated, it just doesn't seem to know what to do?
    I've heard talk of a failed diode? Any testing repair help appreciated as its low mileage any unlikely to failed mechanically.
     
  2. Qavion

    Qavion F1 World Champ
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    Feb 20, 2015
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    Ian Riddell
    #2 Qavion, Nov 8, 2024
    Last edited: Nov 8, 2024
    Could be the plastic gears in the motor/gearbox have failed or are lacking lubrication. It could also be corroded or failed sliding contacts or, as you say, a diode failure. If it's trying to move, it may not be the diodes.

    If it's something like the 456M headlight with a large round plug, here is the setup:

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    i.e. there are two wire motors (possibly brown and green) and 3 direction control wires, blue, white and red. Power on the blue wire drives the pod up until the sliding contacts switch over to the down contact. Due to diode polarity, the pod stays in the up position until the lights are switched off.

    First try winding the pod up manually a little with the knob (keeping your fingers well clear of the moving parts). It may move the sliding contacts into a non-corroded area (or move the gearbox past missing teeth) and the pod may come to life. Note that you have to turn the knob a lot to get any mechanical movement.

    There's not much you can do about broken gears, but corrosion can be removed. In some cases, the metal contact "fingers" can be repaired. There are pictures showing motor/gearboxes disassembled on the 456/550/575 forum.

    The diodes are usually hidden under the sealant and you have to dig them out.
     
  3. cptn.Big

    cptn.Big Rookie

    Nov 17, 2008
    17
    #3 cptn.Big, Nov 9, 2024
    Thanks very much for all, I should be able to diagnose from the info you have provided. I will reply once sorted out.
     
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  4. cptn.Big

    cptn.Big Rookie

    Nov 17, 2008
    17
    #4 cptn.Big, Nov 29, 2024
    RE; '95 456 head light drive assy.
    So, based on the wiring diagram supplied, I removed and bench tested the assembly after having continuity tested all connections, and couldn't get any reaction. With nothing to lose, dove in and disassembled it completely. Obviously this is not something designed to be repaired as the coating is a S.O.B. to remove and beware there is an unprotected green wire buried in it that you have to be careful not to damage or it will require replacement. (not a huge deal) Once at least partially exposed, I found the gear case cover is riveted in place, but with some gentle prying the cover can be removed. Fortunately or not? everything inside was pristine and well lubricated with still very good grease. That being the case I tackled the motor, again not designed for disassembly, is it is held onto the case with three split tangs that have to be bent together to allow removal. Once apart, again all looked pristine, bearings, armature, brushes etc., the diode is inside the motor case so not in-bedded in the outer coating as some have suggested.( other modes/yrs?)
    Having found nothing whatsoever wrong I used the old mechanics last resort solution, reassembled the whole thing, reinstalled it, and now it works perfectly.

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  5. Qavion

    Qavion F1 World Champ
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    #5 Qavion, Nov 29, 2024
    Thanks for the update, cptn. Not sure why the differences regarding the diodes.

    Glad it all went back together again. Did you adjust any of the external linkages. I don't know if the geometry of those might prevent movement.
     

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