I have done the search, and looked around but the damn tach is still MIA. This is on a 1983 GSL. As per the searches, I have checked trailing igition and ignitors. Or as I thought, here is what I did.
I pulled the trailing wires, put them on a spark checker, and while engine is running getting good spark on both trailing plugs. So that means that trailing ignitor, coil and all are working. Took both wires running to the coil, + and -, cleaned terminals and wires and connectors, especially - as this is supposed to feed the tach. Still nothing.
Pulled the instrument cluster. checked the connections, looked good. Also, Speedo, oil pressure, volts, and temp working. Fuel is not working but that is to be done after tach, always need the next project lined up.
Anyway, pulled the cluster. Put a voltmeter in the harness, specifically yellow w/green wire and had voltage. Now the funny part. Pulled the glass off the instrument cluster, all the gauges when moved would manually reset back to resting place. EXCEPT tach. I am still wondering is there something that I am missing? Something else to check , or some other area besides a bad tach? I am doing this on a budget, so if I can get around a tach, hoping a wiring or connection problem. But not looking good. lol
Also, how do you change the tach? I could get the needle of the tach, but the voltmeter needle would not come off. Didn't try very hard as didnt' want to break it. But anyway, might just be easier to swap whole cluster.
Also, there is a metal box on the back of the cluster, that is rusted on the outside, with two wires coming out of it, green w/ white, both going to what looks like grounds on the back of the cluster, what is this. Right in the middle, sooooo anychance this has anything to do with tach?
Thanks

Travis Nelson

 

I have the same situation as you, and also have not figured out the problem. So if anyone can give an answer, that would be good for both of us.

 

Just had a brain fart. Would the tach unit itself come out of a 86 2nd gen and go into the gauge cluster? I have one of those, but could disassemble the cluster and take out the tach, put it in my 83 cluster, and work if they might be compatible. Orrrrrrrr, I have a cluster out of an 81, any reason that would not work on my 83????

Cheers,
Travis

 

hey i got the same problem too, have no clue what the problem is some one help us out thanks

 

Had the same problem for months. I was told both igniters were fine, so I replaced the cluster but it didn't help. Finally, out of desperation, I replaced the trailing igniter. Tach's worked ever since.

 

the tach may not return to its original position because it is of the floating magnet, dual transverse field coil type.

in english, this means there is no return spring, and the little rusty box calculates the bias applied between the transverse coils to deflect the movement...
check connections, and use a DMM to see if a good AC voltage can be detected on the tach input line.. if not, there is a wiring/ignitor problem.. if there is, the unit itself is faulty.

 

So I should have AC volt. coming out of the tach signal wire at the cluster?
Also, did anyone know if the tach from a 2-gen 1986 NA will work in this cluster?

Thanks in advance,
Travis

 

yup, AC voltage from the signal wire at the cluster connector, and the FC tach should be compatible, unless it gets its signal from the computer.. the signal from the coil "-" is very messy, with high voltage transients (which destroy computer tachs.. trust me).. obviously a signal from the computer would be well behaved.