I got a vintage Stewart Warner 970 tach with a 990 sending unit. I want to install this on a 69 Roadrunner with a new 426 crate gen 3 Hemi motor and the M+H engine harness, the one with the orange distributor box and black electronic voltage regulator with duel field alternator. Any Idea's on how to wire? Do I pick up the red wire off the ignition switch? How about what side of coil to use? The yellow wire before the ballest resistor or after?

 

i have am old Stewart Warner tach. it might be the same as yours. i bought mine in 1967. but it is broke. and in pieces. it is a 0-6,000 RPM. not even sure i know where it is. if i can find it you can have it.

 

Thanks for the offer, but I got a tach and Inow got a set of instructions so I'm good to go. Thanks sincerely Brian

 

The problem, here, is you seem to have the destructions and I don't. I don't remember how these old Suns were wired.

Most tachs need a trigger off the points. There are a few that were actually wired in series with the positive coil feed.

If your ignition has a 4 terminal ballast, you need to determine which (two) terminals are the ignition feed. This will be the end of the ballast with the two terminals jumpered together.

If you have a two terminal ballast, the ignition feed is easy. Just unhook one end, turn on the key, and use a test lamp to see which lead is "hot."

Normally, a tach needs a trigger off the points, and in the case of a Mopar ECU, this is the coil NEG terminal.