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Master cutoff switch

H

HWess

Member
Installing a master cutoff switch on all the tractors. Should I break the ground wire or the hot wire with the switch?
 
Looks like Will and John below need a tie breaker.

Do either one- it really doesn't matter.

That certainly clears things up, doesn't it?
 
I did all mine on the ground. They work great. Many are the ones from harbor freight with the removable plastic keys. Thought I might have some problems, but none in 5 years. I think they were only 5 or 6 bucks. I put the larger ones with a throw lever on larger tractors or trucks.
 
Ground. The positive would spark. Think about how you hook up battery cables. Hook up the positive first and it won't spark without a ground.
 
I don't think it matters, but if you break the ground then when you put a wrench on the hot clamp and the handle of the wrench touches the frame it won't spark. Same reason you always disconnect the ground first and re-connect it last.
 
Ground. Here's why.

Typically, the switch is mounted to the frame of the tractor. Inside the switch there are two contacts and a rotary "knife blade" that connects and disconnects the two contact posts.

One of the ways these switches can fail is to have the knife blade contact the metal parts of the switch. This essentially connects the battery cable to ground.

If ground cable is being switched...no big deal. If the hot battery cable is being switched...lots sparks and possible fire. Been there....done that...

K
 
I put one in the military vehicle I just finished. It's on the ground wire so I don't have to worry about anything making fire if it touches the bare connections on the back of the switch. It makes choosing a location for the switch easier. Jim
 
Which ever is most convienient to the location chosen for the switch. Never use it to shut off the equipment. Serious electronic dammage will occur if it has an alternator, or other electronics like a transistorized distributor. Jim
 
Placing it on the ground cable will isolate the battery from being grounded. That's where the military had them. Hal
 
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