Hello folks,

I would really appreciate some help with this issue...

I noticed that my passenger side break light goes out when I press the break pedal, but only while the running lights are on. Also when the running lights are on, if I turn on the driver's side turn signal the rear passenger running light goes out (same bulb). No problem if I turn on the passenger side turn signal.
When the running lights are off the break light works fine.

One other thing: the emergency flashers seems to be blinking extra fast. They hardly have time to go dim before the light up again. It's like we're at a rave.

I am aware that the bulb in question has two elements: One is for the running light and the other is for the break light. I've read that my problem has to do with the extra voltage or the two signals at once that are supplied to the bulb when I press the break while the running lights are on. Essentially, when the running lights are off and I press the break, the bulb is only getting the one signal. If the running lights are on and I press the break then the bulb gets two signals at once and goes out due to a grounding issue.

I've replaced the bulb. I've replaced the bulb socket. I've pulled the ground from behind the taillight and sanded the body and reinstalled the ground. I' going to continue to mess with it, but if you have any suggestions I'll take 'em!

1974 f100 2w
240 i6 c6 auto

Thanks,
Dustin

 

Check and clean all grounds.
Battery to block
block to frame
Block to firewall
Front light grounds (passenger side is in between the battery tray and core support)

Most lighting problems can be traced to grounding issues. (check those first)

Also make sure the bulbs and sockets are good.

 

Thanks John! I went through a ton, making sure things were good section by section and finally got it.
Fuse box connections in back were rusted.

Cheers!

 

Did that fix both problems?

Thanks for letting us know the fix.
Dave. ----