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Red Warning Light

Discussion in 'Norton Commando Motorcycles (Classic)' started by steveyacht, Oct 8, 2019 at 6:28 AM.

  1. steveyacht

    steveyacht

    Joined:
    Aug 11, 2009
    The red warning light on the headlamp shell of my '73 750 is not working. Does not come on when ignition switch is on and engine not running. I checked the connection inside the shell, all appears to be ok. What else should I look for to get this working again.

    Thanks.
     
  2. maylar

    maylar VIP MEMBER

    Joined:
    May 13, 2007
    Inside the headlight shell: battery power (white wire) to the bulb, the other wire (white/brown) goes to the Warning Light Assimilator under the tank. The assimilator grounds the bulb (probably a red wire) to turn it on without the engine running. If you ground the white/brown wire the bulb should light.

    So... a voltmeter is your friend.

    And, maybe check the bulb?
     
  3. jsnorton

    jsnorton

    Joined:
    Oct 10, 2018
    Is your battery fully charged ? , check with a test light or volt meter the wires going to the bulb, if you have power there check that the bulb is not burned out. Try switching the key on and off a few times also. If the key switch is original it may need cleaning.
     
  4. steveyacht

    steveyacht

    Joined:
    Aug 11, 2009
    Battery is fully charged and switch has been cleaned..... used a bit of very fine emery cloth to get better contact. I have a volt meter and I will check the bulb. If not the bulb, I will not get any more involved as I don't want to remove the tank. Thank you all for your responses!
     
  5. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    Hi Steve,

    The aluminum can warning light assimilator is fragile. They break inside often. Replace with either original or the solid state one.
     
  6. steveyacht

    steveyacht

    Joined:
    Aug 11, 2009
    OK, checked the voltage at the lamp connections, no problem, same voltage as the battery. Stupid question, how do they come out? Yea, I know this sounds really dumb, but..... consider the source. FYI, from what I can see they are the original units. Where can I get replacements?
     
    Last edited: Oct 9, 2019 at 10:15 AM
  7. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    Andover Norton in England has both type. Easy to do online ordering. I don’t have they website at hand, but you can do a search.
     
  8. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    I didn’t answer your question how they come out. The original position of the warning light assimilator is under the gas tank connected to the coil bracket on a large spring. The spring is to isolate this fragile part from engine vibration which works for some time. I got tired of the aluminum can type breaking and went to the solid state type which was used on the 850 MkIII.
     
  9. motorson

    motorson VIP MEMBER

    Joined:
    Nov 29, 2011
  10. Gadge

    Gadge VIP MEMBER

    Joined:
    May 21, 2019
  11. maylar

    maylar VIP MEMBER

    Joined:
    May 13, 2007
    If the voltage at both lamp connections is the same, then the bulb is likely OK (prove that by grounding the white/brown wire) and the problem is likely with the control gizmo called a Warning Light Assimilator. The gas tank has to come off to access that. I believe the bulb holders (sockets) are a press fit into the headlamp shell.
     
  12. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    Not sure if you rechecked bulb yet. You can easily pull the fitting out of the black plastic surround that holds it in the headlight shell. The then remove bulb from its socket rotate the bulb while pushing in against the socket spring. Rotate until it wants to pop out as the tabs clear the socket grooves.

    Yet another option to replace the assimilator device is the SparkBright Eclipse LED voltage indicator. It fits the existing hole in headlight shell and gives great info on charging state while running.
     
  13. steveyacht

    steveyacht

    Joined:
    Aug 11, 2009
    I may sound like a fool, but I am not able to separate the plastic surround from the bulb. I have given up because I fear breaking it. I will simply leave it the way it is. Thank you ALL for your help
     
  14. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    So to clarify, you have not actually tested the bulb and are unable to remove it from the socket? You can try some penetrating oil or WD40 to help loosen the bulb in the socket. Bulb needs to push in and then turn until its metal bayonet tabs can clear the socket groove for it to pop out. These bulbs can be replaced cheaply if you need to take more drastic action like breaking the glass then using a tool to grab the metal to force it out.
     
  15. maylar

    maylar VIP MEMBER

    Joined:
    May 13, 2007
    I think he's unable to get the bulb out of the lens holder.
     
  16. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    He should still be able to confirm if the bulb is working by connecting power to the socket terminals directly. Seems odd to test all the assimilator circuitry etc before confirming if the bulb is good.
     
    maylar likes this.
  17. steveyacht

    steveyacht

    Joined:
    Aug 11, 2009
    Let's back up and regroup. First, there is power the wiring that feeds the bulb. Second, I am unable to remove the bulb from the lens holder. I Have not removed the tank in order to test the assimilator, nor do I see a need to being as there is power to the bulb holder. Being as I am not able to separate the lens from the holder without possibly damaging it, I am going to leave well enough alone...… leaving the charge warning light inoperative. Hope this clarifys
     
  18. lazyeye6

    lazyeye6

    Joined:
    Feb 28, 2014
    Nortons can be quite odd and seemingly impossible to work on at times. Taking a deep breath and coming back to a problem
    another day with a fresh perspective has always been successful for me. That and listening to good advice. We have all been
    there.
     
    steveyacht likes this.
  19. steveyacht

    steveyacht

    Joined:
    Aug 11, 2009
    Oh! I get it! I put this one together out of the Crate in 1973 Helped refurbish her around 12 years ago or so. Cantankerous is the word that comes to mind.
     
  20. maylar

    maylar VIP MEMBER

    Joined:
    May 13, 2007
    Does the bulb light when you ground the white/brown wire?
     

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