by Adrian Worman » 23 Jul 2013 8:42
Yes, poor ground on the tail light issue, the fault could be just with the grounds from the rear light clusters .
If cleaning and making good the ground doesn't help or only helps a little bit then you have a poor ground somewhere in the entire lighting circuit, so check headlight grounds, sidelights, even the light switch itself.
The tach is fairly easy, if the coil was bad the car won't run so you can eliminate
Check the wiring loom carefully, I'd suggest checking out the wiring schematics at the top of this section.
Jesus built my hot rod