I bought a reproduction engine harness, and the gray tach wire is included. It’s taped into the harness. Is that right? I thought the tach wire was run separately if the car came with a tach. I don’t remember ever seeing an unused tach wire (at the coil and bulkhead connector) on cars that did not come with a tach. Thanks in advance for your help.

Gray wire is for clock power. You need a separate tach harness to run tach out to alternator and coil.

Here is an example: Link

I found a picture of an original 70 RR in the Moparts archive, and its tach wire looks like it is taped into the harness. That confuses me. The parts book only lists one harness, but it seems strange that the wire would be there on cars without a tach. My car did not come with a tach, and I’m not sure if the harness that was on my car the original one or not.

I was typing when you replied😆. I’ll look at your link.

I was referring to the gray wire in the engine harness. Doesn’t it go from the coil - through the firewall grommet, and then to the tach?

The gray wire in main dash harness is power for the clock only. You need a separate harness for the tach as suggested above. The gray wire in the lighting harness is for hood mounted turn signals.

The repro engine harness has the tach wire built into it.An original or NOS engine harness the tach wire is seperate from the harness.

Thanks for your reply. I figured that had to be the case. I’ll just take that wire out of the harness, the way it’s supposed to be.