My ‘07 Sportster doesn’t have have a tail light and just has bullet style 3 wire, dual filament 1157 bulbs used as run, brake, and turn signals on the rear. The problem I just started having for some reason is that whenever I press the front or rear brake and have either the left or right turn signal on, the rear turn signal won’t flash with the brakes on. The front signals work fine. As soon as I let off of the brake then they start flashing again. Any ideas what could be causing this?

 

Sounds like your two wires in the rear socket are probably touching inside housing below the bulb contacts.

 

Sounds like the brake/turn/running light module may be having issues.

 

+1

 

RIPSAW, do you think the wires are touching each other or touching the inside of the housing itself?

 

Each other. Touching housing would blow fuse. Unhook wires and use ohm meter on bulb contact to other . Also check bulbs. Vibration does strange things. I had that little disk contacts wires go into and thru crack. Also had it happen on trailer lights and it went to housing. Took out the diode splitter module instead of fuse for signal, brake, taillight on a foreign truck with yellow signal lights. $30 part rather the a 25 cent fuse.

Post 3 will also do it when diodes go bad.

 

I removed the left rear turn signal bulb and shined a light inside the socket and noticed that the plastic piece that wires go through that the bottom of the bulb touches was partially behind the spring inside the socket. I tried to pop the spring back over top of it but didn’t have any luck, so I’ll have to remove the whole turn signal and try it that way. I’m betting that when the bulb is in the socket, part of the bottom of the bulb is touching that spring. I wonder if that could be the reason why signals won’t flash with the brakes on?

 

Twy22, did you resolve the problem? What was it?