Bizarre electrical problem

[kesteven]

My 1997 R1100RT developed a strange electrical problem on the way to work this morning. When you turn on the ignition, only the upper ABS lamp illuminates on the indicator panel - no neutral, or battery charge indicator. Bike starts normally. ABS engages with standard whirr/click after a few feet and remaining lamp goes off. With engine running, at idle in neutral the charge light and neutral light glow very weakly. Put bike out of neutral, and neutral goes out as expected. In neutral, pull on front brake and neutral light goes out, and charge lamp comes on strongly. Also, when charge light is on brightly, having pulled front brake, the revcounter falls to zero ( I'm not making this up ! ). All other electrical switches (headlamp, horn, indicators etc.) work as expected, but have no impact at all on the way the problem presents itself. I did fit PIAA 1100X lamps over Easter, but all worked fine on the rides since then, until this morning. I did not touch any wiring, other than to pick up the headlamp main voltage from the headlamp connector. Only one possible idea on something I could have done - I mounted the plastic PIAA relay case using a existing bolt under the tank that fixes the ABS assembly in front of the battery - could have wrecked an earth path - but that doesn't explain why all worked fine until this morning. Anybody have a specific idea on what to look for before I inspect the whole wiring loom and all connectors :-(

[John Ranalletta]

Check your battery terminals for corrosion & loose connections.

[Joe Frickin' Friday]

Also, when charge light is on brightly, having pulled front brake, the revcounter falls to zero ( I'm not making this up ! ).

 

The tach is electrically driven, so that's not all that weird.

 

You've got a bad connection somewhere, one that's not able to provide enough power to light all the requisite lights (and tach) at once. I'd start by undoing your light connections (both the mounting at that ABS assembly bolt, and the splice into the headlight harness). Maybe all worked fine until you got a smidge of corrosion that screwed up a ground path. That's the easiest first thing to try.

 

If all is still SNAFU, then pick up a Haynes manual, which has an excellent electrical schematic diagram in it; that may help you trace the problem.

 

Please clarify: you are powering the actual PIAA lights off of the headlight harness, or you are just powering the switch? The switch would only require a smidge of power to operate the relay, but the lights themselves (as a pair) draw 110 watts, which is a very large additional load to draw from a circuit that was designed to supply just 60 watts to the headlight. I hope the PIAA lights themselves draw directly from the battery.

 

How many miles on the bike?

[bmwmick]

My 1997 R1100RT developed a strange electrical problem on the way to work this morning. When you turn on the ignition, only the upper ABS lamp illuminates on the indicator panel - no neutral, or battery charge indicator. Bike starts normally. ABS engages with standard whirr/click after a few feet and remaining lamp goes off. With engine running, at idle in neutral the charge light and neutral light glow very weakly. Put bike out of neutral, and neutral goes out as expected. In neutral, pull on front brake and neutral light goes out, and charge lamp comes on strongly.

 

Two things to check.

Fuse #1 powers the tach, Neutral lamp, ABS test relay, oil pressure lamp and low fuel lamp. A loose or defective fuse can cause all these symptoms.

 

If you had the large ABS connector off the Hydro unit, reseat it. The ABS voltage test begins when the ABS relay in the fuse box is first energized. The upper lamp is powered separately.

 

Let us know how you make out.

 

Mick

[SnowDog]

Bad ground could easily show symptoms like you describe.

 

You just have to find it.

[kesteven]

Wow ! - Thanks to all for so many useful responses in such a short time. I'll heed the advice and let you know how well I got on with tracing the problem.

[DEF]

Anybody have a specific idea on what to look for before I inspect the whole wiring loom and all connectors :-(

 

Yes, a new bike.........

[Wild Bill]

Try a ground jumper wire directly from the battery negative to the side of the ABS housing... Or un do what you did the next morning... Maybe you disturbed a ground when you were in there. Unless some thing just gave up the gost over night...It is always the last, or second to last thing you were messing with...

 

Best of luck..

 

BK

[kesteven]

Results of 1st after work attempts at diagnosis: Found that fuse #1 is blown(15A). Replacement fuse blew during a short ride - not immediately. Having studied circuit diagrams, all odd symptoms observed seem to be explicable as a result of fuse #1 being blown. Question now is: Why is it blowing ??!

[Joe Frickin' Friday]

Results of 1st after work attempts at diagnosis: Found that fuse #1 is blown(15A). Replacement fuse blew during a short ride - not immediately. Having studied circuit diagrams, all odd symptoms observed seem to be explicable as a result of fuse #1 being blown. Question now is: Why is it blowing ??!

 

Try undoing your PIAA setup and see if the fuse keeps blowing.

[kesteven]

So - I found the problem. The strange effects were all down to fuse 1 blowing, because the brake light switch cable had chafed against a sharp edge at the cable tie point on the handlebar. I'd created the problem by tieing cables when I did the PIAA installation, and not checking for strain when turning the handlebars to both locks. Motto of the story - "Always check the last thing you touched" !