yet another issue, electrics this time.........

[BubbaZanetti]

so here's the scenario:

i'm driving down the highway at about 70mph the other night in 5th, i drop it into 4th to pass a car and there go my instrument lights and tail light. i pull it over, set the key to "park" and they come back on, start the bike up again and they're fine.


last night, i stop w/my friend at a light. thinking i'm gonna blow him off the line (he's got a 01' ducati 750ss, yeah right!) i crank it and shifting into 4th i lose the same lights again, except this time when i get home and turn the key from park (lights on) to the start position i get nothing.

so, is this a vibration at high rmp issue causing a bad ground to shake lose, or is it something to do with the engine speed itself. as i've stated before, this is a pretty ratty bike and the circuit board in the back of the headlight is fairly coroded. after doing some continuity testing, this may be where the fault lies, but i'm not sure.........

[Cosmoline52]

Sounds like what's been wrong with mine for years, I traced it to the ignition switch. Over the years the contacts have eroded from use and vibration (I guess) so when I turn the key from Off to Park, all is well. When I continue from Park to On, the instrument lights and taillight go out. This to me is no big deal since I can ride around daytime with only the headlight on, when I want to turn on the instrument and tail lights I just slightly move the key back toward Park and everything is on again. I learned a long time ago that this shouldn't be done while rolling since it's easy to move it a little too far and kill the engine! :eek

You might try a test, slowly move the key/switch from Park to On and back, noting whether there is a point at which your lights go out again. If as you say you have no lighting now (except the headlight, I would imagine?) and your board is nasty, it could be that lighting circuit from the switch to the board, or from the board to the harness.

You might also check the switch itself, it may have started to come apart which tends to separate contacts from one another.

[CustomSarge]

Switch contacts wear & age. Give'em a shot of contact cleaner & work'em through all their stops. Like muscles; lack of use correlates to inability to function on demand. <<<)))

[kbasa]

Originally posted by flash412
You didn't say what bike. If it has a "nail" ignition key, I can tell you how to fix it.

84 R100S, according to his profile.

[BubbaZanetti]

i found a really loose ground comming out of the relay under the ignition last night, cleaned it, reinserted it and gave it a pinch with some pliers, seemes to be fine now in both park and on. only time will telll though.........


also, how easy to find/cheap are the circuit boards at the back of the headlight, mine's fairly rotten looking and i think may be the cause of a few of my electrical devils????

[Braddog]

I have the EXACT same issue, mine is a 1977 R100RS.

Checked the wiring harnesses(major wires and plugs to/from light assemblies), but didn't check any circuit boards.

My next step was going to be taking apart the light switch and seeing if I could clean it up, although the ignition almost seems to be a better bet, given that the taillight and instrument lights are ALWAYS on in the "parking lights" setting.

Help me here, folks.

Relay under the ignition switch up top? Or down under somplace?

Also, where's the circuit board at the back of the headlight? Remember, I've got the RS fairing to work around as well.

[CustomSarge]

A lot can be done to restore a circiut board before replacement is necessary:
0> apriori : cost of replace must significantly exceed that of repair (quality of new most always >>> repaired).
1> remove & "lightly" ScotchBrite it. See if actual trace corrosion is happening: a> if not, spray w/silicone & replace, b> if so, replace board OR rebuild traces w/wire & solder recoating (an electronics type can do this).
2> further assistance would work better if I had pix of scenerio.

[qualifier: >20 yrs circuit board work experience] Good hunting <<<)))

[Braddog]

Ok, just for fun, it works for me as well when I slightly move the switch back to the park position, meaning everything's on. While the majority of my riding is done during the daylight hours, it's not uncommon for me to ride to work in the morning before the sun comes up. I'd really rather have my taillight commuting in traffic. I also don't relish the idea of tweaking the switch just a tad in order to have all my lights.

This tells me that the most likely candidate is in fact the ignition switch. Tomorrow, I will take it out, try some contact cleaner, also make sure that all of the other plug connections are clean and shiny.

I probably won't go to the circuit board behind the light until that looks like a likely option.