No Brake Lights when Headlights on? Help...

[SoCalHarley]

I have a '91 Softail that has a weird problem. When the the switch is in the Ignition position and the headlights are off the brake lights and directionals work perfectly. When I switch to the Headlight position the brake lights won't work but all other lights function normally. Any ideas would be appreciated.
Buzz

[shoveldog81]

That is weird - I've got a 92, so it should be similar.  I'd suggest you check the plug that goes from the rear lights to the front - there's a plug right near the battery.  I'd do some continuity checks there.  Then I'd go the ignition switch.  And trace down the wire that connects to the terminal that works the headlights and see where it's messed up.  Harley, at some point put a jumper between two of the ignition switch leads so that it works like the newer bikes, where even the "ignition only" position turns on the headlights.  My 92 came with that, but I removed it.  The wiring is actually pretty simple - I'd think it's got to be something between that ignition switch and the plug that runs to the rear of the bike.
Dog
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[SoCalHarley]

Yea, I removed that jumper probably twenty years ago.  I tried adding it back to see if the brake lights would work in the igniton postion but jumpered so the lights would be on but no luck.  I think I am gonna get a new electronic ignition switch and see if that does it and if not I will trace the wires as you described.  Thanks for your help.
Buzz

[Old Crow]

If you have a bad ground in the tail light, you'll have either the brake light working or the tail light working, but they both won't work at the same time.  This is because it's using the other filiment in the bulb as a path to ground and when you apply power to both filiments, it just goes out.
Check your ground.  Especially if everything else works normally.

[ridemyEVO]

Is it possible the running lights wire and the brake light wire under year rear fender are touching from a frayed wire? You gotta think brake light works by itself in ignition position and no runninglight/headlight but when you switch to lights on the ignition switch you now have both being powered. I disconnected the jumper on mine as well.

[KB]

 

If you have a bad ground in the tail light, you'll have either the brake light working or the tail light working, but they both won't work at the same time.  This is because it's using the other filiment in the bulb as a path to ground and when you apply power to both filiments, it just goes out.
Check your ground.  Especially if everything else works normally.

bad earth