Tach issues, any ideas?

[MoparMike13]

Hello,

So I've been trying to get everything on my dash back to being 100% functional, already replaced the clock, speedo, and all the light bulbs. The only thing that's preventing my dash going back together is the darn tach.

I figured that the original tach broke a long time ago and someone replaced it with a column mounted sun tach just to save time, it was functional but I personally wasn't a fan of the look. I ordered a repop one from OER and figured it would be as easy as plugging it into the stock plugs... nope, no movement whatsoever. So I figured something was wrong with the dash harness, I followed the signal wire (grey with a tracer) back to the firewall and everything looked fine, looked in the engine bay and noticed that there was no wire plugged into the corresponding slot. I take the signal wire that was running directly to the sun tach and plugged it into that slot (slot 20, I believe), thinking that would fix my problem and.... still dead. I tried searching for directions for it (as it didn't come with any) and stumbled across Summit Racing's Q&A section for the tach, where they replied saying you need signal, ground AND 12v, unlike the original which just had two connections. I pulled the OER tach back out of the dash, made some quick connections in the engine bay to test it and completely take the dash harness out of the equation. I hooked up the sun first to verify my wiring was good and it worked just fine, then I hook up the OER and still NOTHING.

What am I missing? I can believe that there might be a short/issue with my dash harness, but why would it still not work when wired directly from the negative side of the coil, 12v and ground (wiring that the sun tach worked perfectly fine on)? Did I just get really unlucky and get a defective tach from OER?

I'm completely stumped at this point, so any ideas would be great.

Thanks,
Mike

[Romi]

MoparMike13,
Read through this thread, there's a lot of info sprinkled throughout. I just read it today.
https://forum.e-bodies.org/electrical-and-audio/11/engine-wont-fire-when-tach-wire-hooked-to-coil/589/

[JS29]

  @Romi Nice first post, your hitting the ground running! 

[Cuda Cody]

Welcome @MoparMike13  to the forum!     Can you tell us more about your car.  Is it a new restoration with all new wiring or are you using original wiring?  Is the car stock or does it have some modifications?  Points or electronic ignition?

And nice first post @Romi   

[Chryco Psycho]

Welcome to both Mopar Mike & Romi from Panama 

[MoparMike13]

@Romi: Thank you, I'll definitely read through that thread.

A little more info on the car, I dont know a ton as I think it's done the typical runaround through several individuals
and dealers before it ended up with me.

The car was restored at some point in the past, looking at the condition of the paint (rock chips, a few dings, scratches), I'd guess that was at least 15-20 years ago. It looks to have been a fairly extensive effort as the underside of the car, frame and engine bay are all in amazing shape. Most of the car is very stock, especially the interior. I really believe the dash (and most of the rest of the interior for that matter) was never removed from the car. The only major modification done to this car was an engine swap, this was a factory 383 car and, I'm assuming when all the restoration work was being done, was swapped to a 440. It has points ignition, I've checked the wire running from the negative side of the coil and can't see any issues there either, aside from the fact it was unplugged from the firewall and run directly to the Sun tach through a grommet. I believe my stock dash wiring harness is in pretty good shape, all the other stock gauges and lights work perfectly, which is why the tach has me stumped.