headlight problem

[Air Ready Auto]

So I had Lucy out for a few hour ride today. Put on about 140mi. About half way through the trip I start smelling something not quite right. I pull over and see some smoke wafting up from the fork area by the key hole. I check everything over and don't see anything noticeably wrong. I keep riding and the smell goes away. A little while later one of our boys in blue kindly let's me know my headlight is out. Hummm. My high beam works but the low one is out and when I switch to low the smoke and smell return. Any ideas on what to start with? A quick inspection of the wiring doesn't look like any frayed or shorted connections.

[cowpuc]

Did the white light on the dash come on,, I have had to replace the Reserve Lighting Unit a couple of times thru the years.. Think if it was mine I would pull the headlight and check RLU and the wiring leading to the low beam terminal on the headlight.. You might be able to find the fault visually either by just looking at the unit and wires or by flicking the switch and looking for a little smoke.. Funny thing is, it sounds like something went to ground - sure seems like you'ld of popped a fuse before you started melting stuff...

In the end, an ohm meter may be necessary to ohm out the wiring to find out where the short is..

[Black wing]

my old venture used to burn the plug on the low beam, its usually a bad ground that causes the heat. check the head light harness and see if there are any bad connections to the frame.

[Marcarl]

Oh Oh, you let the smoke out. Bet that wire is cooked.

[Air Ready Auto]

Did the white light on the dash come on,, I have had to replace the Reserve Lighting Unit a couple of times thru the years.. Think if it was mine I would pull the headlight and check RLU and the wiring leading to the low beam terminal on the headlight.. You might be able to find the fault visually either by just looking at the unit and wires or by flicking the switch and looking for a little smoke.. Funny thing is, it sounds like something went to ground - sure seems like you'ld of popped a fuse before you started melting stuff...

In the end, an ohm meter may be necessary to ohm out the wiring to find out where the short is..

 

So which one I the low beam terminal and what does the RLU look like and how would I know if it went bad? Also, none of my dash lights work and somebody did a bang up job wiring around my fuse box so I only have two fuses in there. One for the starter and one for something else I cant identify.

[bongobobny]

The Reserve Lighting Unit (RLU) is a black box about2" x 3" with several wires coming out the end, and is mounted on your front fairing frame in the middle top behind all those relays across the front of the fairing frame. It's function is to detect if and when your low beam is burned out and automatically switches over to the high beam and lights the white light on the dash. If your high beam was not lit when your low beam went out I would suspect it was indeed the problem source and possibly the source of your smoke.

 

I agree with Black Wing though, the plug for the headlight often goes bad mostly due to corrosion leading in increased resistance resulting in the plug actually melting somewhat, so give it a good look see first, but by your symptoms, i agree with Pucster about it being the RLU. Not sure if they are still available new but they exist as used and come up on Fleabay quite frequently or check with Pinwheel parts in Ohio, they are a pretty big motorcycle boneyard and are reputable but IMHO a little high on their prices but not really ridiculously so...

[Patmac6075]

Wait.....What? I don't mean to hijack this thread, but did you say the white light on the dash is normally supposed to be out?, Mine stays on all the time (I have thought it was distracting while riding at night)????

So, I guess I have some sort of problem?

[bongobobny]

yup!! Probably either your RLU, OR either your low beam is out or one of the two tail light bulbs is out (or a combination thereof). Yes, the white light will come on if one of the two tail light bulbs is out if I recall right, but haven't driven the '84 since '08...

 

Another remote possibility is an issue with the reed switch that senses the total current draw for the lighting circuit but that is rare. Pull the lense off of the tail light first and see if both bulbs are lighting, then onward to the headlight...

[Air Ready Auto]

So I played around with the wiring and didn't find any burnt wires and all of the plug-ins on the headlight look clean. Put everything back together and now the low beam works and the little white light on the dash is on... went for a short ride and the headlight flickered twice in about 15mi. Still thinking RLU?

[Black wing]

that almost says it is for certain the rlu, the two things i would do to rule out any other fault would be to replace the head light bulb and the fuse as well as check the fuse holder for corrosion. if the problem persists after doing that your RLU is on its way out for sure.

[bongobobny]

You did check your tail light bulbs, correct?? That will cause the white dash light to be on if even one of the bulbs is out.

 

But the smoke you mentioned sure does sound like the RLU... Was the white dash light on before the smoke letting incident??

[Air Ready Auto]

that almost says it is for certain the rlu, the two things i would do to rule out any other fault would be to replace the head light bulb and the fuse as well as check the fuse holder for corrosion. if the problem persists after doing that your RLU is on its way out for sure.

 

I only have 2 fuses in there. One for the starter and one for something I can't identify. I do not see any corrosion on what is left. Someone did a "I'm an electrician" job on my bike...

[Air Ready Auto]

You did check your tail light bulbs, correct?? That will cause the white dash light to be on if even one of the bulbs is out.

 

But the smoke you mentioned sure does sound like the RLU... Was the white dash light on before the smoke letting incident??

 

Tail lights are all good. None of my dash lights worked till I took the front apart to check the wiring to the light.

[bongobobny]

OK!! Double check the connectors to the dash, but it is sounding more and more like the RLU...

[Black wing]

well for sure you need to find where and how the head light circuit was patched and get a fuse in there. the corrosion in the join may be causeing the flicker and if you can smell burning the fuse should have popped and likely is the cause of the rlu failure. before you replace the rlu fix the fuse or you may cause another unit to break

[Doug royal86]

where is the rlu my white light goes off sometimes but stays on most the time. All the lights work.This is my 3rd mk1 first time I had this happen

[Flyinfool]

The RLU is about the size of a pack of cigarettes and is located behind the windshield and under the dash, or you might be able to get to it thru the headlight.