Electrical Problem- Help- !!!

[bdavanza]

I rode my bike about 170 miles on friday and it was typical highway for about half and then delicious tree lined East Tx farm roads the rest of the way.
When I got there I used my battery to inflate an air mattress and charge my phone. The bike started fine. The next day it didn't have enough juice to really start the bike, it would turn over slowly but not go kapow.... I have experienced this before and blamed my decision to abuse the battery. Someone had one of those small portable "jump start" kits whose battery could not be any bigger than the one on my bike, so that got me started. I took it for a mmm 10 mile ride and it was running great. When I brought it back, someone noticed the tail light was dimly lit. I checked it and it was dimly lit, even though the key was out and the ignition switch was off. I disconnected the fender harness from the bike for the time being, and now that the bike is home, i have had it on a battery tender for a day.
Any ideas why the taillight could be getting this small amount of volts?
-Ben

 

[BlueJ]

Stock taillight? Sounds like you've got it miswired... or a fault in the switch that's supposed to turn that thing off when the key is out.

 

[drlapo]

you have pinched wire=ground fault in the light circuit
use a multi meter to find it
disconnect the tail light harness and test the wires for a ground fault to isolate the problem

 

[bdavanza]

It's not a stock tail light, it's a Lucas style aftermarket. It's worked fine for a year or so.
Now that the battery has had a chance to recharge I can do some investigating. It just seems really odd that there could be power to the light with the switches off.

 

[biker7]

Who did the wire job? Aftermarket harness or did you make it? There is no way the tail light should be dimly lit with the key out unless its miswired. Non of the leads in the harness are hot with the key off. If the light is properly wired downstream of the connector under the seat then you have a short upstream or an issue with your ignition switch. You need to chase the small millamp drain upstream of the harness which is dimly lighting the rear tail light until you find where it is shorting to the batt and why.
Good Luck,
George

 

[bdavanza]

biker7
I made / updated the sub harness myself but I did it right with solder and shrink tube. That's a good point about no hot wires with the key off. That is what was so perplexing to me. I will look at the switch harness, it was relocated to the side by the PO, and there is some withering electrical tape. I wish shrink tube could magically stretch around connected wires.... Nonetheless, the wires and light have been fine for a few years, something must have changes, like insulation rubbed raw or something.

 

[biker7]

Sounds like you kinda know where your problem is and doesn't sound like it is rearward of the connector under the seat but in front of the connector. If you think about it...it can't be rearward as no matter how messed up the rear harness could be, it can't get power to the light with the key off unless something is afoul in front of the connector. Its a pretty easy thing to chase.
Identify the hot wire with small current using a multimeter...attaching the mm right at the connector with black MM lead to ground i.e. frame. Then chase the colored wire forward. It has to be grounding off of a constant hot connected right to the battery. If you have a service manual on CD...helps a lot as well.
And yeah...no magic on a sloppy wire job...a pitfall in fact of buying a modded bike if the orginal owner wasn't fussy about wiring. I have changed a fair amount of wiring on my new EFI bike and have a lucas rear light which I like a lot as well. You will figure it out and sounds as though you know where the issue is.
Cheers,
George

 

[bdavanza]

magical fix?

I went in to look at it last night, and reconnected the tail light harness. No glow. hmm. It's been on the battery tender for 3 days now. I started the bike, and revved it a bit, got it warmed up, all is well. Shut it off, no glow. Put the seat back on, and rode it brit bike night at the Amsterdam. A couple of pints and a pizza later, I checked on it again, then rode it home in the misty night. Still no glow.
Could it be that when I was trying to start it on a weak battery that a relay partially stuck on? You know these electric start bikes can do some weird stuff when they crank over on a low battery, like that annoying rrrrrrr sound. I will be keeping an eye on it.
-Ben

 

[biker7]

I went in to look at it last night, and reconnected the tail light harness. No glow. hmm. It's been on the battery tender for 3 days now. I started the bike, and revved it a bit, got it warmed up, all is well. Shut it off, no glow. Put the seat back on, and rode it brit bike night at the Amsterdam. A couple of pints and a pizza later, I checked on it again, then rode it home in the misty night. Still no glow.
Could it be that when I was trying to start it on a weak battery that a relay partially stuck on? You know these electric start bikes can do some weird stuff when they crank over on a low battery, like that annoying rrrrrrr sound. I will be keeping an eye on it.
-Ben

Don't think so Ben. Starter relay and solenoid are not in the circuit for your rear tail light. Power is directly from the batt through the ignition switch to the hot wire for your rear tail light. The warm glow you speak of is telling. This suggests a partial short as you aren't getting a full +12VDC to the light which is creating partial and not full illumination. I believe you were on the right track before...the wires you spoke of up in front aren't insulated too well. The other issue is the ignition switch itself or associated wiring. Your ignition switch maybe either internally shorting...with some resistance...or the wiring associated with it isn't insolated causing a short. This is most plausible as the ignition switch is wired directly to the battery.
I haven't had my igntion switch apart on my new bike but word is they can be disassembled. A wet switch can cause this issue as well as water and/or corrosion can induce a mild short with the key out...it doesn't switch completely off in other words.
Hope that helps,
George

 

[bdavanza]

Well that makes sense because it was in constant rain for 12 hours. Problem solved. Maybe I should put some better insulation on the switch and wires down there.

 

[biker7]

Actually pretty common Ben with many different bikes. There are also contributing factors. Many relocate their ignition switch and in doing so shoot themselves in the foot. The right way to do is to extended the 6 leads with shrink tube maintaining the connector inside the headlight bucket. Many don't do that however. For expediency, they simply pull the connector out of the bucket. Exposed connectors...even those relocated under the tank which is another frequent mod...aren't designed for environmental exposure. Those are the bikes that report the highest frequency of shorting out. There is another nuance with the ignition switch worth mentioning. Some mount the switch face up on a custom instrument bezel which look pretty cool. The downside there if caught in the rain is the switch will wick in moisture increasing failure rate. The switch tumbler is deliberately mounted vertically to reduce moisture ingress and maximize drainage.
Cheers,
George

 

[Kirkus51]

Aren't we all glad that we don't have Lucas electronics on our bikes anymore? NYUK!!

 

[koifarm]

Hail to the Queen!

Hah!! Lucas Rocks!!!!:lol::bug::wtf::huh:

:sidecar:

 

[biker7]

Aren't we all glad that we don't have Lucas electronics on our bikes anymore? NYUK!!

I actually had a fair amount of british sports cars and motorcycles with Lucas and really didn't have too many problems with electronics. The new bonnies are wired pretty reliably...only issue I don't like which I changed was I added a couple of diodes in the turn signal indicator position to run more generic LED to dial in the illumination I wanted. Diodes to separate turn signals at the indicator light are common and this was a short cut measure by Triumph. Further...Triumph runs three separate grounds down the rear fender which is needless, adds weight and cost...surprising.
The biggest surprise with the new EFI bikes in my opinion as outstanding as they are, is many leak oil in not one but many places. This is reminiscent of the old bikes in my experience more than the electronics.
Cheers,
George

 

[bdavanza]

I love the old Lucas alternators, you can run with no battery, 12 or 6v off the same alt, no moving parts, timing marks built in, wet or dry. I learned 12v wiring the British way and I have to think twice when working on negative ground stuff.
The worst thing plaguing British bike wiring from the 60's-later was the owners, and those lousy bullet connectors.