[AT] Farmall starter switch

[Claude]

Starter current does not go thru ammeter. Too much current.

Claude

Sent from my iPad

> On Jul 23, 2014, at 9:56 PM, "Dean Vinson" <dean at vinsonfarm.net> wrote:
> 
> Nuts.   Got to thinking, "That might just be a bit too easy," so I went back
> out, reconnected the starter cable to the battery, and touched the other end
> of the cable to the bare post on top of the starter motor.   Big sparks but
> no response from the starter motor--so my theory that the switch simply
> wasn't making contact appears to be incorrect.  Time to take the starter
> motor off, but that's a task for another evening.
> 
> Before doing anything tonight I'd once again tried to start the tractor
> normally, and watched the ammeter while doing so.   Nothing.   Ammeter
> deflected just fine when I turned the lights on, so I'd assumed the lack of
> any noticeable deflection when I pulled the starter switch meant there was
> no current flowing and the problem was in the switch itself.   But bypassing
> the switch sure didn't get that starter motor moving.   Did make a new
> little arc divot in the top of the post on the starter, though.
> 
> Dean Vinson
> Saint Paris, Ohio
> 
> 
> -----Original Message-----
> From: Dean Vinson [mailto:dean at vinsonfarm.net] 
> Sent: Wednesday, July 23, 2014 9:22 PM
> To: 'Antique tractor email discussion group'
> Subject: Farmall starter switch
> 
> 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
> 
> 
> 
> 
> 
> 
> 
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