Funky Electrical Issue

[stopsign31]

So the tail / stop lamp on my '94 Elite doesn't work. When I plug in a spare tail lamp assembly, it lights right up as soon as the key is turned on -- but now the electric starter will not work. Plug the original tail lamp back in, the starter works perfectly, but no lights. Hopefully some one of the forum has a starting point for my troubleshooting Thanks guys.

[Trafficjamz]

It sounds like the starter relay is not getting the signal it needs from the brake lever switch.

Maybe the old burnt out tailight assembly is shorting to ground and that is why it lets the starter activate.

Check your brake lever switches first and report back.

[Bear45-70]

The system doesn't work that way. The brake light circuit supplies the 12 volts to the starter relay and the start switch supplies the ground to activate the relay which in turn activates the starter.

[Trafficjamz]

get a test light and see what is going on at the starter relay when the bad tail light is in.

[mousewheels]

Odd problem - below may not be the problem, but its easy to test for.

Test:

• Unplug the spare light assembly, then try starting.
• If that works, now turn on the turn signals and try to start - no start? -- see below

-- explanation --
Possibly there is a power or ground side wiring high resistance fault (thin red wire off battery, black wire - +12v switched or thin green ground wire from battery to frame)

1) Starter working with no tail light/no brake light means the relay coil is energizing ok, and generally, the Brake/start button relay are functioning.
2) *Not working* with the spare light assembly installed (and lights on) raises the current flow in the above mentioned wires. Higher resistance than normal can cause a voltage drop sufficient that the starter relay will not pull in.

[stopsign31]

Thanks a million for the detailed asnswer Mouse. Upon further investigation, I opened up the tail lamp assembly to discover that the green ground wire was stretched and violently pulled apart from it's male connector blade. I went ahead and swapped in the replacement assembly that I had and everything is working great now. Thanks to all forum members who supported.