[Farmall] More M electrical problems

[szabelsk at gdls.com]

You definitely have a short in the switch. The reason the one screw is 
getting red hot is because it's carrying all the current from the battery 
to ground. A battery can provide 10 times its rated current under a dead 
short. So if you have a battery that's rated somewhere around 30 amp, 
you're delivering about 300 amps through the screw to ground. More than 
enough to make it red hot. Take the switch off and physically look at it. 
Work it by hand and see if the main contact is making contact with the 
case when it moves. You may find something out of alignment, or something 
worn, that you can easily fix.

Don't know if it's anything like the switch on my Cub, but years of taking 
the battery cable on and off loosened everything up a bit and the last 
time I put the battery cable back on, the wedge shaped contact on the 
inside would rotate when I tightened the nut (almost 90 degrees). It 
didn't short out against the case because it has insulators on each side, 
but I knew I wouldn't get proper contact with the shorting bar during a 
start. A little JB weld fixed the problem, the wedge is now permanently 
positioned.

Carl Szabelski



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