Vintage SW tach issues

[Tiger Joe]

I just finished up the resto on my 69 Chevelle, and i wanted to install the original late 60s Stewart Werner Greenline Tach.

this tach is one of the ones that used the separate little box to connect it.


the issue i am having- the tach works, however the readings are a bit erratic. sometimes it will read idle rpms correctly. but then when you rev the actual engine RPMs dont match the tach reading. or then when it drops back to idle, it will read high.

basically the readings are off someway. is there any testing or checking I can do? or it is just old and needs restored by someone?

[SuperNovaSS]

What model tach do you have installed? If it has a adjustable redline pointer than is requires a separate sending unit called an ignition monitor. Don't run it without a monitor or it will fry itself in short order.


Jason

[Tiger Joe]

Yes it has the separate monitor (what I do technically called the little box). I think it’s a 960 series IIRC?

[SuperNovaSS]

I reread your original post and realized you already said it had the separate box. They made 3 different versions of the box for different ignitions. There was a 990a, 990b , and 990d. What monitor are you running and what ignition are you running?

Jason

[Tiger Joe]

The monitor and tach were on the car from 69 I don’t know which box it is but it would be correct as it from the same car.

Its stock points ignition.