Tach, What tach???

Ok here is the situation.  I have had my car since late December, and ever since I got it the tach has never worked properly.  I would say that it doesn\'t work at all but it does sorta.

Here is what it does.  You start the car, and it reads 0.  You accelerate, and it stays at 0.  However when you punch the throttle (doesn\'t matter what speed) and the car down shifts like it is supposed to, and you can hear the engine, then the tach suddenly comes to life, and shoots to the redline. then you get off the throttle, and it goes back to 0.

Now I haven\'t checked anything except the wire. I did this by un-plugging the Green wire that comes out of the primary coil.  In any case when I did this the tach never worked at all, so this leads me to believe that the wire is good, and that either the coil is not sending a signal, or the tach in the instrument cluster is ****ed up.  

Any input on this situation would be greatly appreciated...and everybody should know that I am not in a big hurry since I have the auto, and that means the car does most of the work for me...I just want everything to work properly.  I am close to going full ricer and getting an aftermarket tach...but I need to find a place to make it look less ricerish. (and if I do this I will probably run it off the second coil since I know that one of them must work)

EDIT also the car has 120,000 km\'s on it, it is a fully MKII (87), and it has no digital dash. I don\'t know if any of this matters, but I guess it could...

Its got a twin coil setup right? Try and take the tach wire and switch it to the other coil. Because the 2nd coil only comes on under a load (I think). That might be why, but I dont know. My tach works.

The only problem with hooking it to the exhaust coil, is that under load there is that 4000 rpm cutout, so after 4000 the tach would probably either cut out or stay at 4000 while the motor could be spinning faster.  But you could hook it up that to see if the gauge itself works.  Course, I don\'t think normally with the auto you would even hit that high.

Well, maybe it is already on the exhaust coil. Thats what I\'m getting at.

I guess that is possible. is it also possible that the primary coil may not be working at all, or only part of the time??? I will have to cheack this out this weekend, or the next sunny day, whichever comes first.

Thanks for the guidence 8)

It could be the grounds for the coil transformers, they go right to the inner fender.

It might also be the connection at the back of the tachometer itself.

Here\'s what I\'d do.

Unplug the exhaust coil. Fire up the car. If it starts, you know your primary coil is at least there, so the ground should be good enough to drive the tach.

Swap the transformers, and see what the tach does. If it\'s still unchanged, then it\'s time to start going point to point on the wires.

Wait a second.  The coils are grounded through the brackets that they attach to on the chassis.  This may be my problem.  Stupid Canadian rust...AAAAAHHHH