New headlight problem

[Pagman]

After I removed the fairing off my '86 k100, I needed a headlight. I decided to buy dual headlights with 55/60w bulbs each. I've been riding with the adjustment for about a week. Just recently, the 55s stopped working on both lights, but the highbeams and park light still work. I plugged in the square headlight of the fairing just to rule out a problem with the dual headlight. Same thing, the 55w doesn't work. Could it be that the wire (i believe it's the yellow one) burned out because it couldn't take the load of the dual lights?

[motodude]

I'm having difficulty visualizing dual headlights on a K100 but, there's no way I would power two 55w headlights via that yellow wire with the current going through the switch, etc.  Use relays for this application.  It would probably work for a while.

One way to tell if your yellow wire is not carrying any current is to check that slot on the connector, or wherever it connects to the bulbs now, with a test light or dvm.  Plugging it back into the original headlight is another way assuming you know that light works too.

You may want to check the handlebar switch when searching for the problem.

Tom

[frankenduck]

Sounds like your headlight switch is fried...

Headlight Relays   

[Pagman]

I'm having difficulty visualizing dual headlights on a K100 but, there's no way I would power two 55w headlights via that yellow wire with the current going through the switch, etc.  Use relays for this application.  It would probably work for a while.

Now you can visualize the dual headlights...
http://www.custommotorcyclepic.com/bmw/bmw-scrambler-k100.htm

I have the exact same headlight

[Pagman]

Sounds like your headlight switch is fried...

Headlight Relays   

Oh man, it sounds like that could be it. I was going crazy trying to figure out a diagnosis. Thanks for letting me know and for providing the link. I'll work on getting a relay.

For a new headlight switch, do I have to buy the entire unit containing the switch housing and buttons? Or is it a replaceable part that I need? What about the switch on the right side? Your link says I have to replace the left, but the left is for highbeams. What confusion! :o

[frankenduck]

What country are you in? (Hint: Update your user profile with your location and put the year/model of your motobrick in your signature please.)

Since you mention a headlight switch on the right (which US bikes don't have given the requirement for the headlight to always be on) then I guess you're not in the US unless somebody swapped in a "Euro" switch on the right hand side.

If your high beam still works then the headlight switch on the right is working since that's what feeds power to the hi/lo switch on the left side.

If you were running two 55W bulbs through the yellow factory wiring then I'd check that wire for melted insulation.  It's barely big enough to handle the current of one 55W load, much less two.

If the hi/lo switch has failed then you'll need to replace the entire left combo switch assembly as the hi/lo is not separately available.

[Pagman]

What country are you in? (Hint: Update your user profile with your location and put the year/model of your motobrick in your signature please.)

Since you mention a headlight switch on the right (which US bikes don't have given the requirement for the headlight to always be on) then I guess you're not in the US unless somebody swapped in a "Euro" switch on the right hand side.

If your high beam still works then the headlight switch on the right is working since that's what feeds power to the hi/lo switch on the left side.

If you were running two 55W bulbs through the yellow factory wiring then I'd check that wire for melted insulation.  It's barely big enough to handle the current of one 55W load, much less two.

If the hi/lo switch has failed then you'll need to replace the entire left combo switch assembly as the hi/lo is not separately available.

I hail from the good ol' US of A. Ok, signature added. I guess I do have a euro switch because i have the option of turning off the headlight completely (i had fun disappearing from my friends at night). I was wondering why that didn't comply with US regulations.

I don't think the hi/low switch failed (dear god i hope not). If i press it up, the highbeams come on. I should have mentioned that when i first discovered that the low beams did not work, i was hearing a bit of static which sounded like exposed wiring. I looked at the yellow wire, but most of it is cover by black insulation. I never traced it because I have to remove the tank if so.

I'm new to using multimeters, but when i tested all three wires, i got the 12v reading from the white and brown wire and got nothing out of the yellow. That's why I assumed the yellow was for low beams. If I got no reading from the yellow, does this mean my wire is bad? or could it also mean that some part of the switch has failed?

[frankenduck]

I'd GUESS that the switch contacts have gone bad.  Many times they go bad just running one 55W bulb through them.  The fact that your high beam works but low doesn't certainly points in that direction.

[DRxBMW]

Sounds like your headlight switch is fried...

Headlight Relays   

Oh man, it sounds like that could be it. I was going crazy trying to figure out a diagnosis. Thanks for letting me know and for providing the link. I'll work on getting a relay.

For a new headlight switch, do I have to buy the entire unit containing the switch housing and buttons? Or is it a replaceable part that I need? What about the switch on the right side? Your link says I have to replace the left, but the left is for highbeams. What confusion! :o

Out of curiosity, check the "flash to pass" function of the HL switch.

If the FtP is working, ___ it's the switch.

I've heard of motobricker's R&R HL switch's but it's damn difficult with NO guarantee, as the contacts melt into the plastic.

Best to buy a new switch assembly and a H4 dual relay for R&R.

[Pagman]

Sounds like your headlight switch is fried...

Headlight Relays

Mr. Frankenduck, I read your link on the headlight relays. Being that I have the dual lights with two 55/60 bulbs, woulld you suggest I use either 14 or 12 gauge wire for this application? I purchased the relays needed for both high and low beams and bought a roll of 14 gauge wire. I just need confirmation that I'm going in the right direction. Thanks.  :biggrin:

[HCorn]

Your load will be roughly 10 amps when both high beams are on (120W/~12V=10A).  The AWG chart says you can run that load with 14 ga. wire for up to 12 feet (out and back).  You're probably fine with 14 ga. since your run is likely less than 12 feet and your load is probably under 10 amps, but you're close to the edge (a 10 foot run could handle 15 amps with 14 ga.).  It wouldn't hurt to go 12 gauge. 

Again, you're probably fine with the 14 ga., but if it was me I think I would go 12 ga.  Plus, less voltage loss = more light.

[Uffda]

I had a similar problem on my K75RT - only the high beam worked for me.  After searching the forums for advice and assuming I would have to find a new switch, I opened the switch and discovered a simple solder bridge had developed.  I was able to carefully cut away the excess solder, reset the two solder points, and button it back up.  Worked just fine after that.  My next purchase was a relay kit from Eastern Beaver.  So, check your solder points for excess flow that essentially hot wires the high beam function, regardless of switch position.

[Pagman]

Your load will be roughly 10 amps when both high beams are on (120W/~12V=10A).  The AWG chart says you can run that load with 14 ga. wire for up to 12 feet (out and back).  You're probably fine with 14 ga. since your run is likely less than 12 feet and your load is probably under 10 amps, but you're close to the edge (a 10 foot run could handle 15 amps with 14 ga.).  It wouldn't hurt to go 12 gauge. 

Again, you're probably fine with the 14 ga., but if it was me I think I would go 12 ga.  Plus, less voltage loss = more light.

Thanks so much for detailing that for me. I'm still learning a thing or two about wiring and voltage, so I'll go with what you suggest. I'll return the 14 gauge wire tomorrow in exchange for 12 and will then begin work with a friend. Bright light, here I come.

[Pagman]

I had a similar problem on my K75RT - only the high beam worked for me.  After searching the forums for advice and assuming I would have to find a new switch, I opened the switch and discovered a simple solder bridge had developed.  I was able to carefully cut away the excess solder, reset the two solder points, and button it back up.  Worked just fine after that.  My next purchase was a relay kit from Eastern Beaver.  So, check your solder points for excess flow that essentially hot wires the high beam function, regardless of switch position.

The headlight needs to be rewired anyway, so if that fails, I will definitely check if there is excess solder like you mentioned. Good to know there can be another diagnosis in case I still don't have success. Thanks.

[Inge K.]

The headlight needs to be rewired anyway, so if that fails,

You still need a functioning switch to trigger the relays, and if the contact points are that badly burnt that you got an open circuit it won`t function.

But it could be that your switch still is able to transport the much lower current to trigger the relays through.

If not,here is a link with "how to" dismantle the switch for examining and cleaning.

Inge K.

[DRxBMW]

The headlight needs to be rewired anyway, so if that fails,

You still need a functioning switch to trigger the relays, and if the contact points are that badly burnt that you got an open circuit it won`t function.

But it could be that your switch still is able to transport the much lower current to trigger the relays through.

If not,here is a link with "how to" dismantle the switch for examining and cleaning.

Inge K.

Burt's pic factorial FAQ link on the HL switch is excellent, especially the last page.  :bang-head:

However, if the contacts have melted into the plastic, there's NO way way to fix it other than a new switch ! ! !

I've also seen solder bridging before, easily corrected.

[Pagman]

UPDATE...

My friend ajay came over today and helped me with the wiring and relays. Being that I know squat about wiring, I sure learned how simple it is once you know a thing or two. Anyway, I stayed with the 14  gauge wiring because it was sufficient. Both beams, hi and lo, were relayed and wired up. However, there was a problem. The yellow wire (lo beam wire) wasn't providing any power. We used a multimeter to check it out and it would not put out a 12 volt reading like the other wires did. It was flat at zero. Being that i had run the dual lights on this wimpy yellow wire prior to placing relays, it most likely became burned out or became defective somewhere. That yellow wire traces into all the other bike's wires it's crossed with and is taped up with the original factory tape (try to picture what the wires look like under the tank). Ajay tested my headlight by cutting the original yellow wire and adding separate wiring to the front half of the yellow wire coming from the headlight connection and touched the other end of the new wire to the fuse. Voilą! The lo beams worked. Hi beams worked as well which means my switch is functional.

NOW, this is what we had to do... we didn't want to go fishing out the yellow wire because then we'd have to mess with all the other wiring it's connected to and that would be time consuming and a pain. So Ajay suggested he attach the wire he connected to the yellow wire directly into the fuse. It was the only option. Unfortunately, that overrides the on/ off light switch. So now, when i turn the ignition, my bike turns on with the lights just like any other modern law complying bike... i thought i was special.  :dunno2: Sigh. The only thing the light switch is good for now is to turn my park lights on and off since those are wired separately.

Although I can't disappear from my friends at night anymore, I at least have lights.

[frankenduck]

There's another option:

Wire a normally closed relay up to the high beam to trigger the low beam relay.  When the high beam is off the low beam will be on.  When you hit the high beam it will turn off the low beam.

(I was short on time once without a replacement switch on hand when a switch went bad and this solved my problem.)

[HCorn]

I'm a little confused . . .

Doesn't the headlight come on with the ignition on ALL K bikes?  In other words, there's no way to turn them off while running (on a properly running K Bike)?

Regarding the yellow wire, on more than one occasion I have just used a jumper when a wire in a harness had a short or open.  Once you've isolated which wire it is, it's generally not worth the trouble to replace it.  Just make a new run.  Which it sounds like what you did.  But I'm still confused about the functioning. :dunno2:

[frankenduck]

Ask your friend who understands wiring and relays.  It's really quite simple.

[w. h. hoon]

the euro. k100 models have an off, park, and on switch on the right side. I would think there was only one power wire to the left side there by pointing to the left switch failure. these can be purchased used if all else fails. then no more wiring nightmares. I am running stock headlight, 12 ga. wire . wow!! what a differance. 

[HCorn]

the euro. k100 models have an off, park, and on switch on the right side.

That sounds like the source of my confusion. My K75 doesn't have an off switch (neither do any of my other bikes).  I hadn't realized some bike do.

[w. h. hoon]

We also have a spring loaded , self-retracting (when weight is removed ) side stand.
The full 66 kw. ( 90 hp.) on my early 85 anyway.
And a speedo that goes up to 240            km/ph            But you ought to see their eyes !!!!
I ended my last post a little strang I guess. I built my own relay system , over the counter relays,over kill on wire size, but I'm all about overkill!!!!!