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Discussion Starter · #1 ·
'94 m900

I have an electrical problem. Basically the fuse for the indicators/tail light/instruments keeps blowing. I have noticed:
1. One time when it didn't blow I wiggled every wire I could find on that circuit, and it didn't blow the fuse.
2. Sometimes it will blow when I am riding, other times as soon as I turn the key.
3. There will be long periods where its fine, then it will repeatedly blow, ie, blow fuse, replace fuse, turn bike on, blow again.
4. One time both the filaments in the tail light blew, I think at the same time. (Brake lights are on a different fuse to the running tail light).

Could it be the regulator, or is it shorting? I don't think its a short because of all the wiggling I did (1.) I think its the regulator because of (4.). In short I really have no idea.

Please any advice/thinking aloud would be appreciated.
 

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I did some work on my tail light (making it LED) and then went riding. When I opened up the throttle I thought I hit the limiter when all of a sudden my gauges stopped working and the bike would not start. I burnt the (I think it was) 15 amp fuse. I had no lights, nothing, it was like the battery was dead. I had a spare 30 and put it in. The bike worked fine. Then I stopped at a light (quick deceleration) and the gauges stopped and the bike would not start again. No lights, no gauges, the bike was completely dead again. The 30 amp fuse was burnt. I had to call for help and I replaced the fuse. The bike started and everything was fine.

When I got home I started a search. I could not find anything but when I called my son out he found it almost instantly.

The wire connections at the brake light (between the light and the frame) would wiggle on accelleration and decelleration and would move and touch the frame. When they touched the frame it would cause a short and blow the fuse.

Where the two wires connect via the male and female connectors, the metal part of the connector is the part that would touch the frame causing the short. I wrapped electrical tape around the connectors and zip tied the wires to keep them from moving.

I have had no problems since (about 2000 miles of riding).

So if you have done any mods or work around the tail light check those wires, wrap them up. Let me know if it worked.
 

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Discussion Starter · #3 ·
I did do some work around the tail light so I'll check that out. Thanks alot.
 

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Sounds like a short; I would check
Indicators
Rear light
General bad/open wiring causing a short.
A look at the wiring in/out of ignition units is also good. 12 years of vibration
could cause problems there.
And, of course, make sure you`ve got got ground from the two major points of it,
battery-frame & motor-frame.
 

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this is why your not supposed to feed them after midnite
 

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Discussion Starter · #6 ·
So a bad ground could cause the problem?
 

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Also check the neutral switch for an internal short directly to ground. The two-wire switch used on the older models can short internally (mine did) and will knock out the fuse for the indicator lights and I think the tail light IIRC. Mine did it every time I shifted out of neutral into first gear.

On the other hand, blown filaments in the tail light bulb could mean unregulated voltage (regulator/rectifier broke). The quick test is see if the headlight coninues to get brighter throughout the rpm range, although they don't always act like that after failing. Check the voltage at the battery terminals with the bike at operating temp and see if it climbs slightly from idle speed to about 3500 rpm amd steadies out at around 13.8V - 14.5V. When my regualtor failed, it worked normally part of the time, but riding at night you could see the headlight suddenyl dim avery few minutes as the VR "clamped" the voltage output from the alternator suddenly frmo a very high amount (like about 15V). Then the voltage would creep up unnoticed until the VR kicked in again in a few minutes. It alos started using lots of water out of the battery.

Electrosport (formerly Electrix) used to have a good trouble shooting flow chart for testing regulators on their website. The Haynes manual does also.
 

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Bad ground will not cause shorts, it`s just a good start to have good ground
and a good battery.
One other classic place to look is where the wiring touches the steering stem.
Many cables rubbing at each other. Not uncommon w a short there.
 
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