R90/6 Electrical Mystery

[reachfar]

I'm wondering if someone can help solve a problem I've had with my R90/6.

Recently I stoped to fill up the gas tank. I couldn't start the bike after the fill up. I turned the ignition key to start the bike again and nothing happened, no indicator lights, no head light, etc.

I let it sit for a couple of minutes and tried it again. This time the lights went on and I was able to start the bike. I flipped on the head light to take off and it died, no lights, no nothing.

I figured I better push it to some place where I could put it under cover for the night and call for a ride (the gas stop had no garage). While pushing it I turned the ignition key several times with no result.

Finally after about 45 minutes of huffing and puffing pushing the bike I tied the ignition switch again and it worked. I was able to ride home, much to my relief.

This is the second time this has happened. The first time it was at my house, similar set of circumstances (lights, etc.). After letting the bike sit over night I was able to start it in the morning.

Any ideas would be appreciated!! Me:

[wecm31]

I would check the harness plug that routes the kill switch to the main wiring loom. If that is backed off, you could have intermittent contact causing the "now you see lights, now you don't".

I have inadvertently worked mine loose while working on the bike and turning the handlebars back and forth to access the instrument pod. Perhaps while filling up the gas you moved the bars full travel?

For my 85 R80, the plug is under the gas tank, right of the frame tube, in front of the coil. Reseating it fully solved all problems.

I don't know /6s at all....If you have "wiring in the headlight" connections, then you probably have that connection somewhere else...

[ccolwell]

Intermittent electrical problems are the worst. It took me four months to solve a similar issue on my Triumph. I doubt filling the gas tank had anything to do with it. The other time it happened -- was the bike warm? If it only happens when the bike is warm/hot and goes away when it cools down, that may tell you something.

I agree that a loose connection is the most likely candidate. Study the wiring diagram to determine all the possible points that could cause this issue. Then spend some time wiggling the wires in all those places until you can reproduce the problem -- at least with an ohm meter. If you can't reproduce the problem, you'll never know if you've fixed it.

That said, there are some other possibilities that I know of. A bad battery could do this. So could a relay. A loose battery terminal or ground (I'm sure you checked this, but I've seen this on several bikes -- and cars).

FWIW, the problem on my S3 was a bad pin inside the multi-connector between the main harness and the ignition switch harness. The pin was the one for the power feed to the ignition switch. I would have never guessed something like that could go bad -- particularly on a modern bike.

[johncarves]

Check your ground cable. I had one that was mounted correctly with good connections, however, it had a hair line crack across one end that was all but invisible. A little bit of movement and the bike would not start. Move it again and the bike ran fine. It finally broke loose on a mountain top in South Carolina. Thank goodness we were in a parking lot, having stopped for a break. There was enough left to wedge under the ground screw (transmission end of lead) and limp home.

[James.A]

A good general practice is to eliminate a weak/sick battery at the start of any electrical diagnosis.

[darrylri]

I had a very similar sounding problem with my R90S. In that case, the clock worked until the key was turned on, then it stopped. The clock uses very little current, so nearly any kind of a connection will pass enough to allow it to function. But with all the indicator lights trying to get juice, nothing worked.

The problem turned out to be the spade connector to the diode board, on the wire that runs to the starter relay. It was not making a good connection and the wire insulation there was showing signs of heat, probably caused by high resistance from the poor connection.

By lightly sanding the spade on the diode board, crimping the female spade connector while free from the diode board and putting a dab of dielectric grease in there, I was able to get better contact, and the problem hasn't returned.

[PGlaves]

In simple terms, you either have a bad battery with an intermittent internal connection, or you have a bad connection or broken but touching wire in the wiring of the bike.

Once you are able to rule out (or replace) the battery then the fun begins.

Since this is not a case of this bulb or that gizmo doesn't work, the problem lies with one of the main connections supposed to carry current to a number of things including lights and the ignition.

Start at the battery and trace the circuits all the way to the coils, cleaning and securing every connection you can find. You may find something so obvious as to be sure you found it, but probably you will never know for sure which connection was just bad enough to fail sometimes.

This is an excellent regular practice, every year or so on Airheads. There really aren't that many connections. Classic K bikes and Oilheads are a lot more difficult, but need the same routine anyway.

On an Airhead this is a good evening or afternoon project. Coffee helps. Beer doesn't, in this case.

[donbmw]

I have had the My R90/6 do the same thing. Clean all your grounds. Battery grounds at battery and where it may hook at the transmission or other spot. All the small grounds under the tank.

Don

[Weasel]

In addition to all of the above - and, if to no avail - it could be a bad ignition switch (the unit that you stick the key into).

The bit with the diode board happened to me once when my R60/6 was about a month old. I called the dealer mechanic and he had me take off the front cover and wiggle the red (I think) thick wire that goes into the diode board. Then, a few years ago when I wasn't riding the R60 much, I experienced intermittent power/no power as you describe. I was all set to buy the iginition switch, but I decided to work the key back and forth about 50 times. That took care of the problem for me, and that was about 5 years ago. It's been fine ever since. I guess the contacts inside the switch had gotten some corrosion on them.

[barron_williams]

Check this out -

http://www.bmwmoa.org/forum/showthread.php?t=48594

As outlined in the thread, I had a very similar sounding problem.

The bottom line for me was -

"The problem turned out to be a damaged section of wire. Specifically, the red (power) wire between the starter relay and the ignition switch in the main harness. It was puzzling, because without a load, I could read 12.9v all the way to connector board in the headlight shell. But, the wire was damaged enough that although the digital meter would read the voltage, the wire couldn't power a load. I fixed it by building a new section of wire from the starter relay to the ignition switch and on to the connector board. I ran the new wire alongside the main harness and through the rubber grommet at the bottom of the headlight shell.

Second, as I asked for help solving the problem, I heard from three folks (two /5 owners and one early /6 owner) who had experienced the exact same failure. This is a heads up to you /5 and /6 folks to maybe ensure you have a yard long stretch of wire with connectors on each end in your onboard parts stash. This would have been a major problem if it had happened in the middle of a ride. But, with the knowledge I have now (and a yard of wire in the tool bag) would have been a simple fix on the road."

That symptom of no lights on the instrument cluster and nothing when you press the starter - dead - seems to be either the battery, the wire leading to the starter relay; or one of the sections of red wire beyond the starter relay, through the diode board, and up to the ignition switch.

Since my incident, I heard from one other rider who had a similar situation, but instead of having an almost broken wire in the harness, he had replaced the diode board recently and the red wire from the battery/starter relay had a slightly loose connection at the diode board so when it got hot, it would "open". Exactly as Darryl describes above.

Hope this helps. I think with the symptoms you describe, one you rule out the battery, it is in one of the sections of red wire.

Regards,

Barron

[beemerPhil]

[QUOTE=PGlaves;713672]Start at the battery and trace the circuits all the way to the coils, cleaning and securing every connection you can find. You may find something so obvious as to be sure you found it, but probably you will never know for sure which connection was just bad enough to fail sometimes.

This is an excellent regular practice, every year or so on Airheads. There really aren't that many connections. Classic K bikes and Oilheads are a lot more difficult, but need the same routine anyway.

QUOTE]

+1 on what Paul said, but as you go along, coat each connection with a thin smear of vaseline("acid-free grease", in your owner's manual).

Do this once, carefully, and you're unlikely to have any more corrosion-related connection problems.....

[James.A]

Remarkably, after replying to this thread, my R75/5 did the exact same thing at a busy intersection. This is what I found when I was safely off the road. I used the binder clip to get a re-start and rode straight home.

[m_stock10506]

Check ground connection very carefully. Also, I believe that your Positive cable goes straight from the battery to the starter relay. Take the relay out and push it back into the fitting several times to make sure the connections are clean.

[85K100LT]

Remarkably, after replying to this thread, my R75/5 did the exact same thing at a busy intersection. This is what I found when I was safely off the road. I used the binder clip to get a re-start and rode straight home.

Please get an odessey PC680 battery. Half the size of the original, no leaking battery acid.

[doktortim]

Wiggle test, force the fault. Turn on the ignition switch, lights on or not, start pulling and wiggling wires. At the typicals. Kill switch, ignition switch, batt cables, every where. When the lights start flashing on and off as you push and pull your onto the culprit.

Intermittent electrical is the pits and this tech will find them most of the time.