MTD 12hp Mower Short Circuit


Old 06-07-05, 10:41 AM
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Join Date: Nov 2003
Location: Montgomery, NY
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Angry MTD 12hp Mower Short Circuit

My 12hp MTD tractor abruptly stopped yesterday due to a rock in the blades. The mower would not restart. My battery was shorted. I tested it with an ohmmeter across the terminals and got zero ohms. I have purchased a new battery and have noticed some strange short circuits. The starter wire post was grounded. I then removed the starter and found that this post is shorted to ground on the side of the starter. The solenoid has a small post (which goes to the switch) which is now shorted to ground on the side of the solenoid. I wonder if I have an underlying short circuit problem here. I had briefly installed the new battery and this, too, was shorted while installed. I removed it and now it is fine. Thanks, Joe Devine
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Old 06-08-05, 01:42 AM
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Hello Joe!

What you are calling a short is just a complete circuit. The starter post will show low ohms to ground because the current goes from positive to negative through a connection. This connection is in the starter, through the brushes. The brushes are connecting the positive post of the starter to ground on the starter armature. This completion of the circuit creates an electromagnetic field in the armature windings which makes the starter turn. Same thing as in the solenoid. The connection you are checking is the end of a wire which forms a coil of wire in the solenoid, then straight to ground. This makes the electromagnetic field that pulls the contact closed in the solenoid to pass current through the larger posts to the starter.

If the positive side of an electrical component had no path to the negative side, then the component would not work. Just like when a headlight blows. All it is is a wire that basically "shorts" the positive side of the battery to the negative, but it's so thin that it glows brightly. When it blows, the "short" is gone (the wire burns in two). But if you check with an ohmmeter across the terminals of the bulb, it will show 0 or low ohms when it's GOOD.
Old 06-08-05, 06:00 AM
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Join Date: Nov 2003
Location: Montgomery, NY
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MTD 12hp Mower Short Circuit

Cheese, thanks! I think my wiring is just a mess after 13 years so I need to rewire the mower. Fortunately I have found the wiring diagram. Thanks again
Old 05-04-07, 02:37 AM
Join Date: May 2007
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Wiring diagram MTD 12hp

Hello Joe,

August 2005 you posted a message with the text "Fortunately I have found the wiring diagram.".
I also have electrical problems and I am very interested in the wiring diagram.
Would it be possible to send me an electronic copy of it (if you still have it!).

thanks for your help,
Ton van der Vliet.
Old 05-04-07, 06:43 AM
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If you have the model and serial # of the mower, you can find manuals which may include a wiring diagram here
Old 07-05-07, 01:28 PM
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Join Date: Nov 2003
Location: Montgomery, NY
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Red face Wiring Diagrams

Sorry for the delay in responding. I have the diagrams and I can send them. If you post your email address, do not use the @ symbol because that can be tracked by folks who would like to get your email ID. The images are jpeg type. Let me know if that is OK. Joe

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