Taillight question

[Semuta]

Hello, I seem to be having a problem with the taillight on my 1974 R90/6. I'm sure it's nothing major, but I would like to know a good (easy) place to start looking for the problem.

The problem: the taillight does not light up when my lights are on, but does when I apply the brakes. I replaced the bulb, but to no effect. Now to be honest, I don't have the owners manual and the switch on the handle bar is kind of tempermental, and I could be turning the lights on incorrectly (I flick the switch up one). If I flick the switch down it also turns the lights on, but doesn't want to stick. Also I don't seem to have brights or normals, just one intensity. Any ideas?

Thanks!

[Junkle]

Hmm. I'm not sure I understand your post (or something may be amiss on your bike).

On my 1974 R90/6 the only switch on the handlebars for the lights only toggles high beam on and off. In order to turn the lights on and off it is on the headlight shell with the key.

Sorry to be of no help but I'm confused as my bike and your post don't seem to line up at all.

j

[20774]

The wiring diagram shows there should be three wires going to the taillight. One is ground, one is from the brake switches, and one is there for what appears to be running lights. Obviously, you have ground and wires for when you apply the brakes. The other wire for running lights goes to the headlight shell and connects to one side of a fuse at #58. This is the source of power. This fuse also powers the parking lamp in the headlight, the speedo and tach illumination lights, and (R90S only) a voltmeter and clock illumination lights. If the parking lamp/speedo/tach lights work, then you've got something wrong with the wire trace from the taillight to the fuse. Try testing for continuity from the taillight to the fuse. Not sure how this wire is routed, but if there's any junctions in the wire on its way to the fuse, you'll need to continue the continuity checks for each segment. Or you could turn the circuit on and probe along this wire, one end of the voltmeter on the wire and the other end to ground. See if you have 12v along the wire...if the 12v goes away, then you've found the section that is broken.

Kurt in S.A.

[jdmetzger]

Hello, I seem to be having a problem with the taillight on my 1974 R90/6. I'm sure it's nothing major, but I would like to know a good (easy) place to start looking for the problem.

The problem: the taillight does not light up when my lights are on, but does when I apply the brakes. I replaced the bulb, but to no effect. Now to be honest, I don't have the owners manual and the switch on the handle bar is kind of tempermental, and I could be turning the lights on incorrectly (I flick the switch up one). If I flick the switch down it also turns the lights on, but doesn't want to stick. Also I don't seem to have brights or normals, just one intensity. Any ideas?

Thanks!

The light switch on the handlebars is center for "normal" headlight, "up" for high beam, and down (where it won't stay) is to "flash", for a pass or something. It's not supposed to stay in that position. When you turn the key ON, the headlight and tail light should come on. If your headlight only works in the "up" position, your low beam is out. Go ahead and get a new 55/60 Watt H4 bulb.

As for the tail light, it's always on, and then gets brighter when you hit the brake. It's a single bulb with two filaments (like the headlight) so the "running light" portion could be burnt out. Buying a new one is a cheap way to check. It's a standard 1157 "brake/taillight" bulb used in cars.

I would try replacing the bulbs before trying to trace some wiring. The taillight is only a few bucks, and the headlight is also pretty cheap.

Now TECHNICALLY, you could have the Euro headlight switch, which would change things, a bit. Based on your description, I'm fairly sure that isn't the case, as the way you describe the headlight switch is just how mine works, as well.

[20774]

He's replaced the bulb once. Unless he's gotten a bad batch of bulbs, maybe one with a single filament, or there's something wrong with the contact points for the bulb, he might have to look more at the wiring. Or even the connector for power in the headlight. What if that connector has come off?

Kurt in S.A.

[cjack]

Hmm. I'm not sure I understand your post (or something may be amiss on your bike).

On my 1974 R90/6 the only switch on the handlebars for the lights only toggles high beam on and off. In order to turn the lights on and off it is on the headlight shell with the key.

Sorry to be of no help but I'm confused as my bike and your post don't seem to line up at all.

j

You're not confused. You got it right. He is not turning the ign key to the lights on position thinking the light switch is the one on the handlebars for the high beam or push down for high beam flash.
UNLESS...some po rewired the handlebar switch to do something else...

[Semuta]

Thank you for the quick replies. I really had no idea that my lights were supposed to come on when I turned the key, as the headlight doesn't do that either. There must be something wrong, a fuse or some wiring or something, with the standard lighting system as the brights work fine. I'll try to replace the fuse, but since electrical stuff frightens and confounds me and I am not really equipped tool- and/or space-wise to do this right now, I might just have to wait to take it to a shop (though there is a 3 week wait at the local dealership right now) and ride only during the day.

[cjack]

Thank you for the quick replies. I really had no idea that my lights were supposed to come on when I turned the key, as the headlight doesn't do that either. There must be something wrong, a fuse or some wiring or something, with the standard lighting system as the brights work fine. I'll try to replace the fuse, but since electrical stuff frightens and confounds me and I am not really equipped tool- and/or space-wise to do this right now, I might just have to wait to take it to a shop (though there is a 3 week wait at the local dealership right now) and ride only during the day.

Well to reiterate, you have to turn the key once for parking lights only, to the next position for ign, again to the next for ign and parking lights and again to the next for ign and all lights. I think that's correct. There are four on positions and one off position on the 74 airheads if I remember correctly. The next year in '75, the handlebar switches were changed and the light switch was on the right control unit. The left side, although different from '74, was still the bright/dim and flash headlight switch.
There is no fuse for the headlights, but there is a headlight relay which can be the cause of no lights if that is your problem and you are turning the switch all the way to the fourth position.

[Semuta]

Yeah, the switch is all the way on, but thanks for the clarification. It gets kind of confusing not having the manual and just kind of winging some of the basic controls. My battery seems to drain pretty quickly also, and maybe these two problems are connected. I'll see what the dealer has to say when I take it in for some other work. I want to get to the point at which I do most of the maintenance myself, but currently live in an apartment without adequate space. Someday . . .

[jdmetzger]

Another good idea would be to join the airhead beemers club, if you haven't already.

http://www.airheads.org

If you go to the website, there is a link to the left under "Main Menu" that says "Email list". It will tell you how to join the airheads list. There are a LOT of very helpful people on that list, who can answer questions from the simple things, to VERY complex issues. Also, if there is another airhead owner in your area, you may be surprised how willing a lot of people are to come and help you out.

Good luck!

[Junkle]

Having run around and around with some basic wiring issues on an old arihead (and I don't think the PO messed up the wiring much if at all) I would highly recommend looking around for some other airhead owners near you. If there is a local club they might have a tech night you could take your bike to. Also check the anon book and see if there is anyone near you offering friendship because if they have had old airheads they might have some insight for you too.

Good luck and don't look at this as a bad thing -- as you work on this bike more and more you will only be making it yours.

j.

[Bigrider]

The next year in '75, the handlebar switches were changed and the light switch was on the right control unit. The left side, although different from '74, was still the bright/dim and flash headlight switch.
.

I'm not sure I've ever seen a light switch on the right control unit. My '76 has both the hi/lo beam paddle switch and what another poster has called the Euro switch just to the right of the horn button, both on the left control unit. In any case, make sure the Euro switch is turned clockwise all the way. My switch was up one click and I thought I'd burned out the bulb or relay, felt pretty stupid when I replaced every thing and then found I could turn the switch one more notch.

Dave H
San Antonio, Tx

[cjack]

I'm not sure I've ever seen a light switch on the right control unit. My '76 has both the hi/lo beam paddle switch and what another poster has called the Euro switch just to the right of the horn button, both on the left control unit. In any case, make sure the Euro switch is turned clockwise all the way. My switch was up one click and I thought I'd burned out the bulb or relay, felt pretty stupid when I replaced every thing and then found I could turn the switch one more notch.

Dave H
San Antonio, Tx

Oh. My bad. The light switch was on the left as you say. Must be I'm so used to the K bikes now.