Yet another LC4 electrical/starting thread

Discussion in 'Thumpers' started by DolphinJohn, Nov 9, 2012.

  1. DolphinJohn

    DolphinJohn Caveman

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    My 2000 640 E is making the loud buzz from the relay back by the battery, starboard cover.

    I rebuilt the starter even though when I opened it up it looked real good. No change. I mistakenly thought it was the starter cable because when I unhooked it from the relay and powered it from jumper cables it would work intermittently.

    I replaced the cable and no change. The battery is an Odyssey and has been ruled out (no change when jumping from my truck).

    I looked at the relay behind the headlight and tried to do a temporary bypass but I don't think I did it right.
    I did notice last night when it was dark out, when I hit the button I can see a spark inside the relay that coincides with the buzz sound from the other relay.

    Also, when I hit the button in neutral with no clutch pulled it buzzes and the neutral light strobes but when I pull in the clutch and hit the button the neutral light goes out and the rear relay just clicks once.

    Would you say it is probably the front relay? (the small white one behind headlight)

    .
    #1
  2. mancunian

    mancunian Been here awhile

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    sounds like the starter motor or rear relay to me, I would try shorting the terminals on the rear relay if it starts no problem then it rules the motor out, if it does not then try powering the starter motor from another battery say with jump leads taking great care, if it then starts it rules the starter motor out. This would be my initial plan of attack to narrow down possible causes, if it starts when shorting the rear relay that points heavily towards the rear relay, but i would check for voltage on the signal cable before replacing it.
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  3. Mo-Tarded

    Mo-Tarded Been here awhile

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  4. bmwktmbill

    bmwktmbill Traveler

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    John,
    Do you have the wiring diagram?
    Is the ground wire tight at the battery?

    Relays are confusing, also the clutch switch and kill buttom and kickstand switch(if present) all add to the problem. I think there should be numbers on the relay terminals so we can figure out how to hot wire it.

    bill
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  5. Donkey Hotey

    Donkey Hotey De Jo Momma

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    It's the battery. Odyssey batteries suck ass. Don't care if the jumper cables didn't help. It's the battery. Everything you described, along with the lights dimming, etc. It's the battery.
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  6. warewolf

    warewolf Tyre critic

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  7. DolphinJohn

    DolphinJohn Caveman

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    Starter motor works fine. When powered from jumper cables directly to the starter it turns fine.

    It does not turn when jumping the rear relay, it only sparks. I was doing this by simply shorting between terminals with a pair of needle-nose.

    .
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  8. DolphinJohn

    DolphinJohn Caveman

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    Ground wire is tight, and all other wires seem good. No sidestand on the bike.



    .
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  9. DolphinJohn

    DolphinJohn Caveman

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    You may be right, although the lights don't dim, just the neutral light flickering along with the buzz at the relay. Headlight, blinkers, tail and brake lights are all real strong without the bike running.

    We put a meter on the battery and there was no significant drop when hitting the button.

    I will swap out the battery from my other bike to make sure.

    .
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  10. mancunian

    mancunian Been here awhile

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    I would also say it is the battery if poor connections are definatley ruled out particularly earth connections.
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  11. DolphinJohn

    DolphinJohn Caveman

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    Is it normal to see a spark inside the relay? (the small white one behind headlight mask)

    .
    #11
  12. Donkey Hotey

    Donkey Hotey De Jo Momma

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    Yes, relays and switches make small, visible sparks.

    Don't waste another minute of your time until you hook up a known-good battery (that actually starts another bike), and make sure it's properly connected with the screws, not just jumper cables.

    I could get into the long-winded discussion of HOW it does this but, everything you've described, I've seen before: normal voltage, no voltage change when you press the button, strong headlight...and it was still the battery.

    I'm telling you: Odyssey batteries are lumps of shit. I will never buy another one. You're chasing ghosts. It's 99% the battery. Go read through the Airhead forum and see how many guys do exactly what you're doing because they're so sure it's not the battery. It was the battery.
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  13. DolphinJohn

    DolphinJohn Caveman

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    It is NOT the battery. :ksteve

    I guess I'm a one percenter. :D

    I swapped the batteries and get the same buzz from the relay, and the Odyssey fires up my F800 no problem.

    I also made sure the ground was good and looked for any other problem with wires.

    I'm going to order both relays.

    .
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  14. Donkey Hotey

    Donkey Hotey De Jo Momma

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    Yes indeed, you ARE the 1% but you HAVE to eliminate the battery first.

    Next step is to short across the starter relay terminals with a screwdriver. If the engine cranks, it's either the starter relay or something upstream. If not, it's the motor or the cables.

    Did you notice any corrosion on either of the cables? What often happens on cars is that acid will get onto the terminals from a leaky battery. The acid will wick down the wires and corrode them down inside the insulation. People clean up the visible part but, corrosion down inside the insulation turns the wire to crap. The same COULD happen on a bike, though batteries rarely last long enough to weep acid.
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  15. DolphinJohn

    DolphinJohn Caveman

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    I tried shorting across the relay, doesn't work. It just sparks. The starter is good- turns just fine when powered directly from jumper cables.
    Positive cable from relay to starter has been replaced. Cables did not have any corrosion at battery.

    .
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  16. bmwktmbill

    bmwktmbill Traveler

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    John,
    Let's start with the relay, does it have numbers on the terminals?

    In your wiring diagram where do each of the wires go?
    bill
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  17. DolphinJohn

    DolphinJohn Caveman

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    Not sure if there are numbers on the terminals. I can look tomorrow.

    The main terminals are battery to relay, relay to starter.

    The two small wires from the relay are:

    Red and white go to the aux relay at headlight area.

    Brown goes to CDI

    I will post photos of diagram- stand by.

    37 is starter relay, 42 is aux relay
    [​IMG]


    27 is CDI
    [​IMG]
    #17
  18. Donkey Hotey

    Donkey Hotey De Jo Momma

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    No point in posting the diagram. You've isolated the problem.

    When you shorted across the terminals, did you get a big spark and did the screwdriver want to stick to the screws or just a weak spark?
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  19. DolphinJohn

    DolphinJohn Caveman

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    Pretty strong spark. Also a bit of a click somewhere.

    An interesting note, when swapping batteries I wanted to check the ground wire once the battery was removed. When I touched the ground nut to loosen it, the ratchet extension must have touched the positive cable and there was a little spark- with no battery in the bike! Is there power stored in a generator or somewhere?

    .
    #19
  20. DolphinJohn

    DolphinJohn Caveman

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    I have??? What is it??

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