Using a Tach/Dwell Meter on a Magneto?

Farmall Cub Forum -- Questions and answers to all of your Cub related issues.

Moderator: Team Cub

Forum rules
Notice: For sale and wanted posts are not allowed in this forum. Please use our free classifieds or one of our site sponsors for your tractor and parts needs.

Using a Tach/Dwell Meter on a Magneto?

Postby Virginia Joe » 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.
Virginia Joe
Cub Star
Cub Star
Posts: 177
Joined: Mon Oct 12, 2009 7:00 pm
Zip Code: 23005

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

Postby John *.?-!.* cub owner » 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.
"The Constitution is not an instrument for the government
to restrain the people, it is an instrument for the people to restrain the
government lest it come to dominate our lives and interests." Patrick Henry
User avatar
John *.?-!.* cub owner
Team Cub Guide
Team Cub Guide
Posts: 19586
Joined: Sun Feb 02, 2003 2:09 pm
Location: Mo, Potosi
Zip Code: 63664
Tractors Owned: 47, 48, 49 cub plus Wagner loader & other attachments. 41 Farmall H.

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

Postby BigBill » 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.
I'm technically misunderstood at times i guess its been this way my whole life so why should it change now.
5+ Years
5+ Years
Posts: 5719
Joined: Sat Jul 22, 2006 5:02 pm
Location: in northern usa
Zip Code: 00000

Return to Farmall Cub

Who is online

Users browsing this forum: AAm, Randy Tuura (RWT) and 4 guests