[AT] Farmall starter switch

[Dean Vinson]

The Super M wouldn't start the other day, wouldn't even show any sign of
trying to turn over, despite plenty of battery power.   Tonight I had time
to take the starter switch off the starter motor (this is a late Super M,
with the switch mounted right on top of the starter motor, rather than
behind the fuel tank support like on an M or early SM).   The spring-loaded
copper contact plate inside the switch and the copper post on top of the
starter motor are both all chewed up where they come into contact when the
switch is pressed.   I assume an electric arc occurs when I make or break
that connection, probably boosted quite a bit by the tractor's 12-volt
conversion, and over time those arcs have removed enough material that the
contact plate simply doesn't reach the copper post any more so the starter
motor never receives the "go" signal.    Anybody ever run into something
like that?  

 

http://www.vinsonfarm.net/photos/SM_starter_switch_post.jpg

http://www.vinsonfarm.net/photos/SM_starter_switch_housing.jpg

 

Coincidentally enough, some years ago the starter switch on the 1950 M I had
at the time quit working--but it was the opposite problem, too much
electrical contact rather than not enough.  I fixed that one by replacing
the worn-out cardstock insulation with some polystyrene modeling sheet, to
keep the moveable switch plate from directly shorting out to the switch
housing:

 

http://www.vinsonfarm.net/photos/M_starter_switch_1.jpg

http://www.vinsonfarm.net/photos/M_starter_switch_2.jpg

 

This time I think I'll look for a replacement switch and hope the post on
the starter motor is okay for a while longer... seems like that'd be the
easiest fix.

 

Dean Vinson

Saint Paris, Ohio