I have a mallory ignition 6al (parts #6853M) ignition box wired up with a sun pro super tach II tachometer. I'm using a mopar electronic distributor with the magnetic pickup.
If I install the tach to the yellow wire (tach output) of the mallory box, the tachometer doesn't work. After reading the instructions it says I might need a tach adaptor. Well the one from mallory is about $115 compared to the one from MSD which is about $50 (#8920). After doing some research on the internet it, it was vague, but it seemed like it should work.
Got it in today, hooked it up and still nothing. Double checked the wiring, even had a spare sunpro tach and tried that. Nothing.
Then I got curious and wondered if I really needed the adaptor. Tried hooking up the green wire from the tach straight to the - coil terminal...still nothing.
With nothing else to lose, I hooked it up to the + side and it worked!! (kind of). The tachometer seemed very erratic while the engine seemed like it was running very smooth. I know this isn't the correct way to install it but can anyone tell me why?
