Well I pulled my gauge in a 88 iroc auto.

I pulled that yellow covered circuit board first on the back of the housing but then realized the fix I have seen here is for the tach itself. So I pulled the tach out and saw the 1-14 pin chip.

I checked the 4-10 Resistance and it was open. SO I wired 2 100k ohm resistors in series to the 2 points and put back together. I will install it tonight. I figure just try something using all others experience here that around 190-200k ohm seems to fix the tach. I think I did a poor solder job but I get around 194k ohm across the points now.

the tach pegs out at 7k immediately so I figure whats the worse happen?

I also cleaned all the surfaces and then installed 4x LED in all the bulbs.

Cross my fingers.