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Thread: Finding high beam wire (under fuel tank?) on 1993 R100RT

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    Finding high beam wire (under fuel tank?) on 1993 R100RT

    I recently bought a 1993 R100RT from my next door neighbor and have been working on getting it in prime shape. I ride in Wyoming's Beartooth range and sometimes find myself coming home at twilight or in the dark. I've seen cows, deer, elk, bear, antelope, coyotes, fox, jackrabbits and eagles in the ditches and on the road (mainly while riding my 2018 R1200 RT). Quite the zoo. This 100RT is (visually) pretty much the spitting image of the 1982 R80RT I bought new 40 years go, so that's fun. I got it so family and friends can ride in the mountains along with my wife and I, and I want them to be able to see any critters in plenty of time.

    I swapped a Cyclops LED lamp into the headlight (a big improvement), but I need more light for the ditches. I took a set of Denali S4's off an F800GS before I sold it, and will be mounting them on the 100's existing front crash bars.

    QUESTION: If the bike's high beam wire is present somewhere below the fuel tank on a '93 R100RT, can someone please tell me where to find it? I see where it enters the harness from the headlight of course, but where does it come out?

    (Note that on this 1993 model, unlike earlier-year models, there are no fuses or other wiring in the headlight shell--the only wiring in there is the leads to the headlight lamp.)

    I plan to get Denali's wiring harness for the S4's (which includes a handlebar switch) and also Denali's DataDim Dual Intensity Controller, and the latter will require a hookup to the high beam lead. So the S4's will be at 100% when I'm running high beam, and at 50% when the headlight is on low.

    I will also need a good switched power source, but I don't expect that to be very hard to find.
    2018 R1200RT, 1993 R100RT

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    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Fixed your “Tags” for improved search ability.
    Good luck and - Welcome to the forum!
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    Registered User kbasa's Avatar
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    Your biggest challenge will be ensuring the alternator has enough juice to run it all. I suspect you won't have an issue because you're using LEDs, but it's something you might want to be conscious of, especially if you're considering running heated gear or grips.

    Good luck and happy riding!
    Dave Swider
    Marin County, CA

    Some bikes. Some with motors, some without.

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    Quote Originally Posted by kbasa View Post
    Your biggest challenge will be ensuring the alternator has enough juice to run it all. I suspect you won't have an issue because you're using LEDs, but it's something you might want to be conscious of, especially if you're considering running heated gear or grips.

    Good luck and happy riding!
    Dave, I'm willing to upgrade the alternator if necessary, but riding around here without a lot more light isn't an option for me. Great lighting and great brakes are must-haves. Night riding is almost never the intention, but still isn't rare. Yellowstone is just a little over an hour away and with so much to see there (and significant distances) it's just too easy to get back after dark. I can easily forego the heated grips, and of course the bike has a good fairing. Maybe a vest can be run, at least intermittently, too, but if not then being chilly for a while beats the heck out of riding half blind. Plus, the S4's, in addition to being LED, aren't the hugest lamps either.

    Oh, then there's the conspicuity aspect. I was riding (the R1200RT) in Cody two weeks ago and someone in a car, sitting behind a stop sign on my left at what was, for me, a through-intersection, suddenly gunned their engine and rocketed forward just as we were entering their path. One would think they were actually trying to kill us. Stopping was no option at all; we'd have been broadsided if I hadn't hit the gas. I suppose we cleared by two or three feet. Fortunately the 1200 had enough umph to get us out of their way but it would have been better to have been in a lower gear. I suppose the (guy?) was drunk or high. Anyway, both bikes are getting more lighting forthwith, front and rear. And I have a renewed commitment to view every vehicle as if they're planning an attack. Complacency is a danger around here because most drivers are responsible and courteous.

    Thanks for the well-wishes!
    2018 R1200RT, 1993 R100RT

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    Registered User kbasa's Avatar
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    Quote Originally Posted by wybeemer View Post
    Dave, I'm willing to upgrade the alternator if necessary, but riding around here without a lot more light isn't an option for me. Great lighting and great brakes are must-haves. Night riding is almost never the intention, but still isn't rare. Yellowstone is just a little over an hour away and with so much to see there (and significant distances) it's just too easy to get back after dark. I can easily forego the heated grips, and of course the bike has a good fairing. Maybe a vest can be run, at least intermittently, too, but if not then being chilly for a while beats the heck out of riding half blind. Plus, the S4's, in addition to being LED, aren't the hugest lamps either.

    Oh, then there's the conspicuity aspect. I was riding (the R1200RT) in Cody two weeks ago and someone in a car, sitting behind a stop sign on my left at what was, for me, a through-intersection, suddenly gunned their engine and rocketed forward just as we were entering their path. One would think they were actually trying to kill us. Stopping was no option at all; we'd have been broadsided if I hadn't hit the gas. I suppose we cleared by two or three feet. Fortunately the 1200 had enough umph to get us out of their way but it would have been better to have been in a lower gear. I suppose the (guy?) was drunk or high. Anyway, both bikes are getting more lighting forthwith, front and rear. And I have a renewed commitment to view every vehicle as if they're planning an attack. Complacency is a danger around here because most drivers are responsible and courteous.

    Thanks for the well-wishes!
    Sounds good, man. I hear ya. Wyoming has LARGE animals roaming around at night. We've got elk here in NorCal, but not in the density you guys have up there.

    FWIW, I have an 05 RT and I put some LED bulbs in the main lights and an HID in the high beam. It's really, really visible with a 2 foot wide arc of super bright white light. I don't ride at night cuz I'm increasingly blind in the dark, but these seem to be decent when I have been out. But few things will give you that big beam like you're talking about for night riding.

    Good luck and safe riding.
    Dave Swider
    Marin County, CA

    Some bikes. Some with motors, some without.

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    Quote Originally Posted by kbasa View Post
    Sounds good, man. I hear ya. Wyoming has LARGE animals roaming around at night. We've got elk here in NorCal, but not in the density you guys have up there.

    FWIW, I have an 05 RT and I put some LED bulbs in the main lights and an HID in the high beam. It's really, really visible with a 2 foot wide arc of super bright white light. I don't ride at night cuz I'm increasingly blind in the dark, but these seem to be decent when I have been out. But few things will give you that big beam like you're talking about for night riding.

    Good luck and safe riding.
    I forgot to mention that when that car came after us, my passenger was one of my grandsons, who's just about to turn ten.

    I also forgot to list bison among the animals on the roads here. They're mostly in YNP, but I saw one 15' off the shoulder of the road outside of the park a couple of years ago. Also had an adult black bear gallop across the road 70-80' in front of me a few weeks ago, in the dark and a light rain. That was on the Chief Joseph highway, nowhere near the park. That took 5 mph off my average speed for the rest of the trip home. :-)

    Now hopefully someone has an idea where to find that high beam wire! If nothing else I may just run a new lead back out of the headlamp shell.
    2018 R1200RT, 1993 R100RT

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    Liaison 20774's Avatar
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    My Haynes shows the two wires (yellow and white) from the headlight going to the light switch on the handlebar and jumper wires off that go to a connector somewhere on the bike. It says connector for "special equipment".
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
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    Fortis Fortuna Adiuvat Omega Man's Avatar
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    A link in this thread may help- https://forums.bmwmoa.org/showthread...urce-Materials

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    Quote Originally Posted by 20774 View Post
    My Haynes shows the two wires (yellow and white) from the headlight going to the light switch on the handlebar and jumper wires off that go to a connector somewhere on the bike. It says connector for "special equipment".
    Thank you Kurt!
    2018 R1200RT, 1993 R100RT

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    Quote Originally Posted by Omega Man View Post
    Thanks OM! This looks like great info and lots of it!
    2018 R1200RT, 1993 R100RT

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    Answer found (was looking for high beam wire under fuel tank, 1993 R100RT)

    Well, I concluded that the high beam wire isn't present under the fuel tank at all. I had begun with the assumption that BMW would not have run full headlight power through the hi/lo switch on the handlebars, and would have had that handlebar switch carrying only lower current to run a relay, which I expected to find somewhere under the tank. But apparently high beam power just goes right from the handlebar switch to the headlight.

    For the new driving lights I wound up tapping into the high beam wire right behind the bulb connector, in the headlamp shell. The new (new to this bike anyway) driving lights work as they should now, dimming to 50% when the bike's high beam is on.

    Thanks again to everyone who offered thoughts.
    Last edited by wybeemer; 09-27-2023 at 06:41 PM.
    2018 R1200RT, 1993 R100RT

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