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Ignition Coil Adjustment
By E.L. (Steve) Stephenson

An inexpensive multi-meter from Radio Shack will permit trouble analysis, repair and adjustment of the Model T coils.  A simple coil holder (see photo A) with spark gap, a model train transformer and your multi-meter are needed, along with 5/16”, 3/8” and 7/16” end wrenches that have been ground thin.  Clean your coils, wood, contacts and points with a little sandpaper.

With coil in hand, test from the bottom contact (A) to lower side contact (B) and read your high voltage winding at a little over 3 Kilohms (3000).  Then test from (A) to (C) with the cleaned points held closed.  This is you low voltage winding and may read about 0.5 OHM.

Then hold the points open with a toothpick and test from (D) to (E) on the high Ohms scale.  The meter should kick and return to near open (2 to 3 Meg Ohms).  Reverse the test leads and the reading should kick and return open as before.  This tests the condenser inside the coil.

If all tests are good, place the coil in the holder.  Hook up the train transformer (see diagram) and the coil should buzz with a nice bright spark (3/16) at the spark gap. 

To check clearances, proceed.  An automotive feeler gauge can be used to set the points.  First use the .005 thousandths blade to check, clean and set the feather spring located under the top coil point spring.  This spring provides “follow” to the contacts, prevents excessive arching and must be free to move.

The actual main point gap should be adjusted to about .030 thousandths or 1/32”.  This can be done by bending on the contact springs at the attachment nuts.

The final step is adjusting the tension nut and coil spring for proper current draw.  This is done by connecting you multi-meter on the AC AMPS scale in series with the lower train transformer lead at the bottom holder connection.  With the coil buzzing, current draw should be adjusted with the tension nut and spring to about 1.5 AMPS.

Four of these coils should let your engine start on Mag and run like a dream.  Remember, don’t touch the spark gap.  It will work fine on an electric fence.

E.L. (Steve) Stephenson