Bizarre main beam telltale problem - BMW F800 Riders Forum & Registry



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  1. #1
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    Hi, all. New to forum, UK based, and I have a challenge

    2015 F800GT. I've had it six months but not ridden much until recently. Impossible to know if the bike came with this fault or not as I've only just noticed it.

    There is a main beam tell-tale or warning light on the dashboard. This is that little blue lamp that comes on when main beam is on.

    Occasionally, when changing down from 6th to 5th, or 5th to 4th, the warning lamp flashes blue for an instant, at exactly the time you change down. Sometimes happens when changing up, too. It only flashes once and its not possible to see if the main beam bulb itself flashes, or if it is just the warning light.

    This fault has defied any attempts to try to reproduce it. Last Sunday, on the outward loop of a 90 mile ride, it happened maybe 8 times. On the inward loop, it hardly happened at all. It not anything that can be reproduced in the garage, of course, and I could go out now for a ride and it might not happen.

    To repeat: it not reproduceable, it only happens occasionally and then only at higher speeds in higher gears and then only at the instant I change down.

    Eternal salvation and a supply of vestal virgins await anyone who can come up with a solution.

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  3. #2
    Richard230's Avatar
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    It is possible that the high beam bulb's filament is going south. Replacing the bulb might solve the problem - or it might not.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  4. #3
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    Thanks: Its a thought. Will try. Will try anything! The fault only happens when I'm daytime riding, so main beam is not actually turned on. I've thought of, but not yet tried, riding on main beam with beam pointing down to avoid dazzling oncomers.

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  6. #4
    Richard230's Avatar
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    My recollection is that the "bulb" warning light on the dash will come on if there is a fault in your lighting system, even if the light is not in use. Another thought is that you might try cleaning the left handlebar switches. Maybe there is some dirt or corrosion in there that is causing your issue.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  7. #5
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    Never heard of this odd problem.

    I would do the following to try to define if changing gear is somehow switching on the main beam or if it's only actually triggering the warning light.

    Remove main beam bulb
    Start bike
    Switch on main beam,
    you should know get an amber warning that there is a bulb out.
    Turn off main beam
    Stop the engine
    Replace bulb
    Start bike
    Switch on main beam,
    you should know not get the amber warning that the bulb is out.
    Turn off main beam
    Stop engine
    Remove main beam bulb
    Take if for a run.
    If blue main beam dash lights but no amber bulb out warning then somehow power is going to the warning light only if blue main beam dash lights and the bulb out warning triggers somehow the main light is being powered.

    Not much help but narrows down what the problem is.
    In the Garage 2013 BMW F800 GT,1994 BMW R80 RT,1986 BMW R80 GS,1999 Yamaha SR125
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    Enjoy the ride 

  8. #6
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    Quote Originally Posted by Richard230 View Post
    My recollection is that the "bulb" warning light on the dash will come on if there is a fault in your lighting system, even if the light is not in use. Another thought is that you might try cleaning the left handlebar switches. Maybe there is some dirt or corrosion in there that is causing your issue.
    From recent work on the bike I know indicator only shows fail when power is applied, if you turn off the indicator the warning still shows you need to correct the fault but power does need to be applied to trigger the amber fail warning in the first instance. I'm confident dip beam is the same. When my failed it did not show the warning with the ignition on but did as soon as engine started and dip beam was powered. No experience of main beam.
    In the Garage 2013 BMW F800 GT,1994 BMW R80 RT,1986 BMW R80 GS,1999 Yamaha SR125
    Sorley missed Honda TLR200
    Enjoy the ride 

  9. #7
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    The main beam switch is on the front of the left hand switch housing as you know.
    I find that every now and again I catch the switch with my glove and either flash the lamp or turn it on.
    Suspect that you're catching the switch with your glove?
    Where are you based? I live near Peterborough.

  10. #8
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    Thanks Richard.
    . Any thoughts welcome. its not the "bulb" warning light, though. It's the main beam indicator or telltale that illuminates normally when main beam is on.

    In this case, main beam is not on, but the blue light flashes very occasionally at exactly the point when I change down from 6th to 5th of 5th to 4th at over 4000 rpm ( very approx.) and is not repeatable. No way of telling of the main beam lamp itself flashes at the same time or if it just the blue light. I've spoken to the non-BMW but highly competent bike retailer where bought the bike and they are as puzzled. They'll fix it, but really need more info to pin
    pin down the fault .

  11. #9
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    Thanks bogbody.
    the bike shop suggested that and that is something I'll look at this weekend. Doesn't fit with the fact that it only seems to happen going from 6th to 5th or 5th to 4th. Still, thanks. It's another avenue to explore. Lincolnshire coast.

  12. #10
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    Quote Originally Posted by MGD109 View Post
    Never heard of this odd problem.

    I would do the following to try to define if changing gear is somehow switching on the main beam or if it's only actually triggering the warning light.

    Remove main beam bulb
    Start bike
    Switch on main beam,
    you should know get an amber warning that there is a bulb out.
    Turn off main beam
    Stop the engine
    Replace bulb
    Start bike
    Switch on main beam,
    you should know not get the amber warning that the bulb is out.
    Turn off main beam
    Stop engine
    Remove main beam bulb
    Take if for a run.
    If blue main beam dash lights but no amber bulb out warning then somehow power is going to the warning light only if blue main beam dash lights and the bulb out warning triggers somehow the main light is being powered.

    Not much help but narrows down what the problem is.
    Good idea, will try. many thanks.

  13. #11
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    The bulb out warning on the dash will go on when riding. As for the blue main beam indicator I think it is either your glove as @Bogbody mentioned or a weak/bad/dirty switch. If the switch leaver is loose enough perhaps it can move enough to briefly turn on the main beam. Possible a bit of conducting trash in the switch. As for bulb failures mine only occur when it raining and I'm a long way from home (days).

  14. #12
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    Quote Originally Posted by FiveBy Five View Post
    Occasionally, when changing down from 6th to 5th, or 5th to 4th, the warning lamp flashes blue for an instant, at exactly the time you change down. Sometimes happens when changing up, too. It only flashes once and its not possible to see if the main beam bulb itself flashes, or if it is just the warning light.

    .....

    To repeat: it not reproduceable, it only happens occasionally and then only at higher speeds in higher gears and then only at the instant I change down.

    When down shifting, the RPMs will surge. This would create a surge in voltage - I'm wondering if the regulator/rectifier isn't always able to immediately handle that surge and system voltage gets higher than it should?
    Concrete remains undefeated. 

  15. #13
    Albervin's Avatar
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    The easiest thing to do is go for a ride at night. See if the high beam goes on/off when the tell tale flashes. Surely cannot be alternator/regulator related as the revs are totally independent of what gear you are in.

  16. #14
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    Thanks all. Lots of things to try...tomorrow!

  17. #15
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    OK Problem solved. I've put a piece of black sticky over the blue main beam warning light (Well, no, I haven't)
    .
    .
    .
    .
    .
    .
    Well, problem MIGHT be solved. Yesterday I paid particular attention to make sure my glove came nowhere near the dip/main/flash switch. Rode 100 miles around Lincolnshire and did not see the blue main beam warning light come on at all.

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  19. #16
    Bogbody's Avatar
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    When I had a little 50 mile ride yesterday I had the opertunity to study the (distinct) possibility of a glove/switch interface while changing gear.
    I'm now of the opinion that a glove could catch the switch and cause an inadvertante lamp operation.

  20. #17
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    Not sure if this is your problem, but I've seen the blue high beam indicator on when there is a broken ground in the headlight shell even with the high beam light off. .

  21. #18
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    Thanks for all the input. Really looks like the problem was caused by glove/switch interference. Went on a 106 mile ride yesterday with 14 others and the problem never arose.

    However, the sensitivity of the rear brakelight switch was commented on loads of times.

    Still, you know the old saying, "as one door shuts...another one closes"

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  23. #19
    Bogbody's Avatar
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    The rear brake light switch is a pain. The microswitch to operate it only needs a slight pedal movement to operate it - about 3mm is enough.
    My mates also pointed out that the brake light was always on.
    When I checked, the slight movement needed means that its easy to catch with your boot - especially with the Wunderlich pedal estendor.
    I've now trained myself to keep my boot clear of the pedal.
    Compared to my old link-braked Honda, the rear brake is weak and only any use at walking pace.
    Heavy application at any significant speed causes the abs to cut in with little effective stopping power.
    Front brake is very good tho.

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