So, my Tach, which has been plaguing me since I bought the car, has a mind of it's own. There's times when it works, and times when it doesn't.

I've already replaced the ignition module (twice, the first replacement was Defective).

The display still lights, but it doesn't light the bars nor send the numbers up or down it reads 0. Then it'll work for a few minutes, then quit again.
The display also correctly goes through the power up test cycle when you first put the ignition into the on position.

I have seen pics off and on, on the forum of a little cylinder on the white wire that goes back to the dash from the distributor. Also I've never actually managed to see the little cylinder on my car, just the wire. Just how far down is that sucker? Is it buried somewhere? The pics I've seen makes it look really close to the distributor yet I've never seen it. Did they get rid of it by 89?
What is that cylinder called? And where can I get one?

My search fu at midnight after working in 90 degree weather all evening is weak, and I'd like to have a working tach, preferably by next weekend.

Or do you guys think the problem is in the dash cluster itself?
I figure the little cylinder, is probably cheaper than the 300 dollars for a new cluster.. especially since I'm not all that fond of the rather...fugly color combo of green and yellow for a gauge cluster to start with, so I'm starting cheap and working my way up.