tach with pertronix

[nmauduit]

Hola!

before pulling the dash I would check the fuse box, it can play funny tricks, esp. with ignition...

good luck !

[oddysseus]

Thank you! Will check.
Is the information I have correct? Power from ignition switch to tach, tach to coil? Ok to bridge terminals on tach?
Odd

[rgh0]

The other common failure point is the anti theft switch in the glove box if you still have it as the ignition supply also goes through this

cheers
Rohan

[RogerFrench]

I'm not sure what you mean, but advise caution!
There's a white wire from ignition switch to coil, via tach. The via at the tach may be a loop around a sensor on the back of the tach, or on later tachs the sensor is inside and there are two terminals, one male, one female. From these terminals you can disconnect the white wires and plug them together, effectively bypassing the tach altogether.
There's little point in doing anything with the outside loop unless you can see actual damage, and I cannot imagine which terminals you could safely bridge.

I suggest you first follow Rohan's tip, then check that the connections are all good and clean. That apart, it would be helpful to know if your tach is standard or modified for Pertronix, and how your Pertronix is connected.
Oh, and also, if your tach is standard it will be RVI or RVC, written on the bottom of the dial. Which is it?