Aftermarket tach reading wrong

[Stale man]

Just hooked up a Autometer tach and have the following:
My scanmaster is reading 1950 rpm at cold start while the Autometer tach is reading 1450. The tach is hooked up to the green plug behind the alternator and the ground is good. There is no setting option on the back of the tach for 4,6,8 cyl. There are 4 wires out of the tach red-power, white-lights, black-ground and green to the plug behind the alt. Is it possible this tach will not work with a TR? Any suggestions are welcome.

 

[TurboDave]

You might want to give Autometer a call. Mine had (if memory serves) a brown wire at the back of the tack (just a little loop I think) that I had to cut to make it work with our systems.

 

[Billdogg]

Yup, you need to cut one of the wires on the back of the tach. Look in the instructions. You usually have to cut 1 wire for 6cyl and 2 wires for 4cyl.

 

[Stale man]

Is the brown wire inside the tach. Do I have to take the tach apart to get to the wire. The only wires that come out of the tach are the 4 that I listed, no brown one.

 

[Billdogg]

What do the instructions say?

 

[Stale man]

I went to the Autometer website and found the instructions. (Guage came with the car, so no inst.) Had to open up the guage and correct the settings. Thanks for the help.