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H/L up and down won't stop

Discussion in 'Technical Q&A' started by great308, Sep 18, 2007.

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  1. great308

    great308 Rookie

    Sep 18, 2007
    4
    #1 great308, Sep 18, 2007
    I have a 1978 308 GTS. It is a great car with an embarassing problem. When I turn the headlamps on, the motor runs continuously causing the headlamp to go up and down and up and down. It usually happens on one side but sometimes on both sides. I have switched out the relays and it make no difference. It would seem that there must be a limit swith that is worn out. Does anyone know how to fix this problem?
     
  2. IanMac

    IanMac Formula 3

    Jul 26, 2006
    1,455
    Scotland
    Full Name:
    Ian
    #2 IanMac, Sep 19, 2007
    This happened to me many years ago on a little Fiat X1/9 and it turned out to be a faulty earth connection.
     
  3. PWehmer

    PWehmer Formula 3

    Oct 15, 2002
    1,733
    Surrounded by Water
    #3 PWehmer, Sep 19, 2007
    Do a search- i recall discussions of a diode going out in the motor can cause this.
     
  4. grub

    grub Karting

    Jun 19, 2006
    101
    Sydney OZ
    Full Name:
    Grant
    #4 grub, Sep 19, 2007
    Mine often did this when I turned them off. Very embarrassing! It was always the front left. Turned out to be dodgy connection on the relay. Cleaned the contacts and all was good.

    But when I initially searched this forum for ideas on the problem, there was lots of talk about a diode in the motor mechanism that can cause this problem.

    As a simple check, clean all connectors going to the lights plus relays.
     
  5. blkprlz

    blkprlz Formula 3

    Mar 24, 2007
    2,169
    Tampa bay
    Full Name:
    Bruce
    #5 blkprlz, Sep 19, 2007
    +1, and don't forget the grounds.
     
  6. great308

    great308 Rookie

    Sep 18, 2007
    4
    #6 great308, Nov 2, 2013
    Thanks all. I caused by the Motor diode, do you have to replace the motor?
     
  7. myronx19

    myronx19 Formula Junior

    May 27, 2012
    653
    Toronto, ON Canada
    Full Name:
    Myron Samila
    #7 myronx19, Nov 2, 2013
    You shouldn't have to - if the diodes are external like the X1/9 (probably the same motor!), then replace the diode, motor should be fine.

    A 1N4001 should do the trick, but you can replace it with anything in that series 1N4007 for example.

    I've never seen them "bounce", more like they get stuck up or down and you have to manually lower/raise them.
     
  8. jacques

    jacques Formula Junior

    May 23, 2006
    877
    Los Angeles/Florida
    #8 jacques, Nov 2, 2013
    Radio Shack has the diodes for $1.00 each. #4001.
     
  9. Ferraridoc

    Ferraridoc F1 World Champ
    Owner Silver Subscribed

    Jun 20, 2012
    17,255
    Gold Coast, Aust.
    Full Name:
    Patrick
    #9 Ferraridoc, Nov 6, 2013
    Had this problem in a GT4
    Turned out to be a loose motor mount - this allowed the motor to rotate a bit so that the contact tracks went hot again and powered the pod up/down.
    Check the mounting bolts - pull the main chassis earth first! The power to the track in the motor is always hot - if it goes off while you're fiddling about in there, you'll break your hand.
     

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