What terminal does the tach connect to

[Derek Greenwood]

I am hooking up an MSD tach adapter in my Scorp. The tach hasn't been hooked up in 18+ years. I need to know if the tach wire normally got connected to the positive or negative terminal on the coil. Per MSD if it connected to the positive it is a current triggered tach. If it connected to the negative it is a voltage triggered tach. The wiring is different based on the type.

 

[dllubin]

If you had a points system, it would likely be connected to the negative terminal. Sometimes when converting to an electronic ignition, the risetime of the firing can be too fast for some tachs to read properly. The manufacturers often have notes on how to pass the signal through an RC circuit to make it friendlier to the tach. My X tach required that mod when I installed a Delta Mark 10B CD ignition.

 

[Derek Greenwood]

I have a 124 electronic ignition with a magnetic pickup

 

[Derek Greenwood]

I have a 124 electronic ignition with a magnetic pickup

But the tach originally was hooked to which terminal. That will tell me the way I have to wire the MSD tach adapter to function with the Lancia tach

 

[Mark]

"D" Terminal

 

[carl]

Every Fiat I have had, points and electronic ignition, had the tach wire to the negative (D) terminal on the coil.

 

[bbrown]

Or, in other words, to the Negative side of the coil.

 

[Derek Greenwood]

Thank you everyone. I wired the MSD tach adapter and for the first time in about 18 years the tach works.