bad ground? electrical issue

[DieselGrease]

hey guys,
i have an electrical problem on my 87 6.9 F250 that I think may be a bad ground, but I'm not sure how to find where the problem is. There are a couple symptoms of an electrical issue in general, but I don't know if they're related:
- My left brakelight/back tail light overpowers my left turn signal. Basically, if I have my left turn signal on when I push on the brakes or have my headlights on, vehicles behind me can't see the turn signal. When the headlights are off and I'm not on the brake, the turn signal looks fine. This only apples to the driver side rear signal.
- The dome light in the cab won't turn off. Even when the truck is turned off and the doors are closed and the switch is off. So far I've dealt with this by just pulling the "courtesy lights" fuse, but I'd rather fix the problem and have the fuse in and my dome light back.
Anybody have an idea where I could start trying to trace the problem, or know where I could find a decent wiring diagram?
Thanks!

[sundownersc]

For the heck of it try running a seperate wire grounding the box to the frame. Sounds like a problem I had years back , solved my issue.

[EMD_Driver]

You may also want to check the headlight switch. They're not known for their reliability.

That one switch does turn on the courtesy light and the tail/running lights..

Gary

[LeftcoastJeff]

When I bought my truck it's owner gave me a quarter and a small roll of duct tape.
He explained that the door switch wouldn't work right without a quarter taped to the door frame.

Does the buzzer sound even with the door closed?

LCjeff