Thread: "Lectrical"

Tweet

I hat it. Seems logic never works here! OK tach not working but did before engine overhaul. Red wire goes to hot term when key is on, black wire goes to ground term under dash, white wire goes to dimmer side of the light switch, and green goes to the tach terminal at the disti.. All connections are tight. I did find that the red was originally connected to a full time hot terminal at the block. I have changed it. I have read installation instructions looking for any fuse locations and there are none. I did go back out there checked the fuses and found the fuse blown on the original red wire hook up. Replaced the fuse changed the red wire and it tach still does not work. Could constant bat. voltage have ruined the tach.
Is there a way to check the tach output at the disti.? I did change the disti. at rebuild. The new one had a blue cap and I had them change it to black. They took an off the shelf cap and switched out the coil. The disti. is a Moroso.

What's make and model of the tach? I'm assuming we're talking HEI distributor?

SunPro (Super Tach II) Yes HEI.

I have been under the dash and noticed that the connection (white wire to light switch gray wire) was coming loose (IDC) connector.

Well, your connections are correct, i.e.,

Red - switched 12 volts
White - panel lights
Black - ground (i like to go to the battery or a chassis ground - not the dash)
Green - Tach terminal on distributor

A couple things:
1. Check on the back of your tach and make sure the cylinder selection is at 8.
2. The HEI coil has three wires. The red one connects to battery, the black is ground, and the yellow one is the tach lead. Check to make sure the yellow lead is firmly seated and that the wire is not broken between the coil and the terminal. Picture below may shed some light.

It is possible to destroy a tach if the ignition is on and the green wire is grounded, but it has to be a hard ground and you would have smelled (or seen) smoke from the tach.

Hope this helps,
Glenn

Thanks Glen! I am chasing it and will let you know what I find. I is hard getting upside down and under the dash in these old cars. But fun!! After I gat this solved it will be getting the speedo working. Classic gages, turbo 400. Looks like everything is hooked up but no speed indication. First things first. Thanks again!

OK I reconnected the white wire going to the light switch and have a light on the tach. Tach still does not work. Is there a signal coming out at the tach connection on the disti I can check for or is it an exploratory operation pulling the top off the disti.

New tach fixed it. Thanks for everyones input.