Just reinstalled a new engine in a car. First turn of the key to on. Tach pegs, blinker light comes. Wires are hooked up properly at the coil.
What gives?

Low battery voltage.

Just took it off the charger. New Optima.

With or without the car running?

Measures 12.8 volts

Not running

Check fuse #8 or #9 ... can't remember which.

checked and rolled all fuses. Bad relay maybe?

No oil pressure or alternator light either.

pull the ignition wire and tach wire off the coil and see if that makes a differeance. do one at a time to test. there is somethign funny in the ignition circuit I guess, and I'd look at stuff that got moved with the engine install (ie stuff in the engine bay)

good luck

I would say coil wires are the first thing to double check.

Also check the 12-pin connector on the relay board. It can be installed one pin off.

12 pin was one of my first things to check.
Dave, already did that too. No difference. I know something is wired wrong, I just can't find it (YET).

OK, Tach went back to normal, blinker indicator glows dimly, and no oil pressure light whith key turned on, but alt light works. I'll keep chasing.

Update: bad oil pressure switch replaced with new, light works. dim blinker light went out, and tach peged again. Owner now tells me its done it before. I'll stick in another tach and see what happens. I did crank the engine and it started on the first turn. Yea!

And just what relay would that be? There are no relays anywhere in those circuits.

The Cap'n

Can you get the coil wires reversed?

Quite honestly I was just shooting in the dark. I already figured that out from the wiring diagram

My buddys car was doing this, turns out his entire harness had melted in the tunnel for some reason and was shorting. Start tracing your wires back from the tach and keep an eye out for anything that might be shorting out.

That was me, It really put a damper on my project, major bummer. The harness was intermittently melted, from firewall to instruments. Luckily, a couple of things, 1. it didn't catch fire 2. I had another car to pull a good harness from. The biggest bummer, I will not go through the stress of installing a harness into an un-restored tub. I do have a tub but it will require some rust repair and a fresh coat of new paint before the re-build. Nuthen like being forced to do it right.