This article is on how to repair a tachometer that is reading too high. The movement of the tach should be smooth, just far higher than actual engine speed. This will not fix a non-working or erratic tachometer.

I made this repair using an article by Oliver Scholz, here. If you would like to know the functioning of the tach and why this repair works, I suggest reading it over. The article contains the information needed to perform the work, but lacks a step-by-step procedure. I wrote a step-by-step on how to perform his repair with the Variable resistor, allowing adjustment of the Tachometer range.

Tools:

1. 7mm driver

2. 5mm driver

3. 10mm driver

4. Torx driver,for interior screws

5. Soldering iron and wire

Parts: 

1. 1mohm variable resistor (potentiometer)

I got this part at radio shack, Part 271-211 It is under $3, and works fine. The only downside is its size. It is like a stereo volume knob, as can be seen in the link. There is still however room to fit it behind the dash.