Using a Tach/Dwell Meter on a Magneto?

Mon Jul 08, 2013 8:48 pm

I recently acquired an old Stewart-Warner Tach/Dwell/Points meter to hopefully determine the RPM's of my running cub. I not sure however, how to hook it up to a tractor equipped with a Magneto. Where would I hook up the red terminal and I assume the black one would go to ground? Can it be used at all with a Magneto? Any and all advice would be appreciated.

PS I do have a Stewart-Warner portable hand tachometer model 757-w but wanted to try the Tach/Dwell for grins.

Thanks for any and all advice.

Re: Using a Tach/Dwell Meter on a Magneto?

Mon Jul 08, 2013 9:33 pm

I have never gotten one to work on a magneto. It depends on interrupted voltage on the point lead, and a magneto does not have external voltage unless it has an external coil.

Re: Using a Tach/Dwell Meter on a Magneto?

Tue Jul 09, 2013 10:39 am

The wire feed for the tach/dwell comes off the grounded side of a distributor, the points are a ground at this time the condenser, condenses the spark so it doesn't jump across the point air gap. This ground wire on the external coil sends the signal to the tach on how many times the points open and close per 4, 6, 8, cylinders. To simulate that a wire needs to go to the points were the ground is. I personally wouldn't mess with a mag too much.