any one know why ?

 

What year is your car? I think on the 79-80 models the tach will stop working if the alt isn't charging. It's a starting point anyway.

 

I also believe on later models the tach will stop working if the trailing coil is bad or going bad?

 

if it doesnt work, especially when cold or all the time... replacing thr whole instrument cluster is what the manual suggests

 

The ingiter on the trailing coil controls the tachometer and also acts as a relay for the fuel pump. You might also check that angle.

 

Check your trailing coil first. That's usually the culprit.

 

A bad trailing coil can also cause an erratic tach.

 

word, the tach on my 79 stayed around 4000 rpm unless i really hoofed it, and when it was cold, the coolant needle showed it overheating when it really wasnt. swapped the gauges and viola!

 

The 79 system is different than the later years and the tach works off of the leading with the point style ignition system. All of the later ones pull the signal off of the trailing side.

Welcome to the forum and the Darkside. In my sig line is a link to the online FSMs,and other rotary related manuals and reading.

 

Verify that you have spark going to your trailing plugs. If you do not the trailing ignitor is bad, this also controls the tach signal. Also check the contacts first at the trailing ignitor. It is the one closest to the engine.

 

trochoid, the 80 also works off the leading coil. FYI.

 

so what if he is getting good spark to trailing igniters? then the coil?

is the tach part of the rubber insulated clip that attaches to the top of the igniter?