Just got my RX-7 finally running, it's up and going amazing.

Except for several minor problems. The first is kind of important - the lack of a tachometer. I do not have a working tach.

The pictures following are part of the wiring harness that goes to the tranny, specifically the wires that go into the bolt that screws into the tranny - these split off the harness about a foot to two feet before said bolt. The bolt has two single-wire female connectors that are free on top of it, as well as the wires shown. Of the wires shown, the two with blue tape on them were stripped for some reason, so we taped them up.

What are the wires for? And although I've searched, the wiring harness on this car is so freaking screwed up that I am having at best extreme trouble tracking down how to get the tach working - do these wires relate to the tach?

 

Tach signal comes off the Trail coil assy. There is a black bullet connector on it that has a yellow wire with blue stripe. That wire is a *maintainance check terminal* that has the tach signal on it also.

The Trail coil wires are of the color in the attached jpg.

IF your trail coil does not spark, that is the problem.

One newer way to prove the tach is good or bad, is to find the similar black bullet connector at the LEAD coil assy. Run a wire from that black bullet connector to the TRAIL coils black bullet connector. Then start the engine. Tach will work if the wiring from the engine bay to the instrument cluster is any good.

By running a wire, I mean bare both ends of the wire and stick one end in one black bullet connector and the other in the other black bullet connector. You should see readily what I mean by bullet connector when you look at the wiring going to the two coil assy's.

IF ONE or two of those wires are colored BLACK/YELLOW, they are power wires with batt voltage on them, and usually feed the Trail coil assy power. Also there is one black/yellow in that area that connects to a black, square condenser. The black, square condenser is bolted to the chassis with one bolt.

 

One thing I forgot to mention, after reading your reply in depth - the tachometer worked perfectly prior to taking apart this car and redoing a bunch of stuff on it.

However, the speedometer and tachometer (and obviously odometer) no longer work after taking stuff apart. We'll be replacing the speedometer cable this Wednesday, but the Tach is still a mystery. I'm going out to try what you recommend right now, however, with respect to connecting the bulet connectors.

 

Yep. Trailing coil was hooked up incorrectly - specifically, a cable was not hooked up. Fixed now.

 

my tach isnt working either so im searching treads for an answer, what year is your rx? im working with an 84 FB

 

It's the yellow/green wire on the trail coil.

This is a second generation forum. The wiring is not the same as on a first generation car as a second generation car.

Maybe, just maybe, the people on the First Generation forum would be of more help on first generation cars. Mabe. Perhaps. Could be, maybe.