Printed Circuit Board

[amloya]

I just replaced the printed circuit board on my 70 Custom 10. Half the dash lights were not working, but all gauges worked fine. Now that I have replaced the circuit board, all of the dash lights work fine, but the brake light (on bottom left side of fuel gauge) works some times and others not. Also, the tachometer works OK if headlights are off but when I turn headlights on, the tach revs up to 4500 rpm and works backwards. When I accelerate, it goes down to 3000 rpm as if it was wired up backwards. This only happens when the headlights are turned on. Any ideas what might be the problem?

[qksilver]

sounds like ground problems

[amloya]

Thanks. Any idea what I need to check? I don't remember disconnecting any grounds when I pulled the dash out to replace the circuit board.

[Longhorn Man]

Did you post the same thing somewhere else? I coulda sworn I responded to this already.
I would start by adding a bround from the dash, to the 'tin' in the back of the inst panel. Just a section of wire with eyelets on the ends will do.

[amloya]

Thanks. I think there were two posts out there, but one must have been erased. What do you mean by tin? Do I need to connect the ground wire from the dash to one of the screws holding the circuit board to the gauges?

[byrd]

No you need to connect the ground wire to one of the 8 mounting screws that holds the tin and the plastic bezel together.

[Longhorn Man]

as long as it is bolted to the metal backing, it won't matter where. Personally, I like putting it where the printed circuit board bolts on and grounds to the tin.