battery disconnect switch

[MSD]

Am going to put a disconnect switch on my tractor. Which is the proper way to do it? Use the ground wire as the input to the switch or use the hot wire? I assume both ways would work.

 

[Dblair]

I used the hot on the tractors I did. had the wiring on an old 450 ground out and catch fire so I do it to all now .

 

[dpendzic]

I switch the hot wire but all my Cat dozers have the ground switched--have no idea of the reason for that

 

[FBH44]

I switched the hot, figured it should be the same as National Electric Code, always switch in the hot, never in the neutral.

 

[JDEM]

Makes no difference. Just make sure it is big enough to carry the staring current. Many of those switches are not. Deere used them OEM on crawlers.

 

[JDEM]

NEC applies to systems with a real ground. Tractors have no ground. Just a NEG and a POS with the chassis often used as a common carrier for NEG.

 

[MSM]

Install switch to disconnect the ground, same as most equipment manufactures do.

 

[Deere Mark]

Most of the battery disconnect switches will only fit the negative post of a top post battery.
The negative battery post has a diameter of about 0.660 inches. The positive battery post has a diameter of about 0.710 inches. ( this is probably done so that you can not install the negative terminal onto the positive battery post, an important point to remember when installing a battery. If you don't remember if it is positive or negative ground, you can usually not get the terminals to fit the wrong way).

 

[Steve@Advance]

Best to use the grounded terminal. It's a safety issue.

When the disconnect is added, it requires repositioning the cable terminal, which could put it in a place more likely to come in contact with the chassis.

And it is safer handling the grounded terminal, especially if wearing a ring or watch, something that could short to ground if touching the non-grounded terminal.

But...

Having a disconnect on the battery itself still presents a very real danger!

Breaking the circuit will cause a spark if there is a load on the battery. If there were an emergency situation, as in an electrical short, hung starter, etc, the battery would be out gassing hydrogen, very explosive! A better solution would be a remote battery switch located away from the battery. More expensive, but safer.

 

[Leroy]

Would not switching the negative put the switch after the potential short and make it impossible to shut off the battery curent that is excaping the wire harnes due to that short to ground. In the negative you would still have after switch was off power to the short that untill battery quit you could not get rid of unless you had cable cutters you could cut the positive at the battery. That is the way I look at it. Put the disconect ahead of any potential problems instead of after. Please explaine why that would be wrong.

 

[John T]

Sure either way will work HOWEVER I always switch the ungrounded conductor. That would be the + battery post source on a Neg ground tractor or the - battery post source on a Pos grounded tractor. It has to have the current carrying capacity of the biggest load IE the starter motor.

John T

 

[JDEM]

RE . . "Would not switching the negative put the switch after the potential short and make it impossible to shut off the battery curent that is excaping the wire harnes due to that short to ground. "

A tractor has no ground. Just a positive and a negative and often the chassis is used as a common carrier for one of them.

If on a modern tractor - the shut-off switch disconnects the battery negative from the chassis - how is a wire carrying positive current going to "short out" anywhere? The battery is take out of the circular loop regardless if disconnected at the positive side or the negative side.

 

[David G]

I would disconnect from the "grounded" terminal of the battery if doing so, but never saw the need for a disconnect.

 

[Pete in MD]

Leroy,

When the switch is on the Neg terminal no power flows in any of the wiring including the starter cable because it has no ground source, it can't get back to the Neg post. Even if you put a jumper from the Pos post to the frame no current can get to the Neg post.

 

[jm.]

MOST older construction equipment broke the ground (AWAY ) from the battery in some remote panel. In affect you are just removing the battery negative cable so takes shorts out of the system. UNLESS the short negative cable from the disconnect back to the battery shorted.

 

[old]

I learned many years ago you always disconnect what ever one is ground. That way you never have a problem with a wrench etc of hitting something and shorting things out.

 

[JDEM]

Deere used them OEM on crawlers like 350s and 450s and those switches prevented many fires. The difference being that the batteries were so far from the engine. Very long run of battery cables in areas where lots of flammable debris accumulates.

That said, I put one on my 1998 Dodge Grand Caravan. It will go dead in a month if the engine is not started unless the battery is disconnected, or a battery maintainer is hooked to it.

 

[Two Dogs]

Then you have never had a starter solenoid points weld themselves together. Ever wonder why airplanes have a master switch? Mine came in handy once for the very reason I first stated. TDF

 

[retired farmer]

I just got four of them to mount on the tractors. Going on the hot wire is what I was told.

 

[9njunkie]

I have 4 now all installed on the negative.... Lots a reasons why to do it that way but it's also the manufacturers directions. That way should a tractor burn up the insurance co will pay out and not say you did not follow the directions.

 

[buickanddeere]

Ain't no neutral on a DC system. No "ground" on a vehicle either inless the term ground = chassis return. Supposed the be ground and sometimes a neutral on AC power systems.

 

[John T]

I do the same Rich, anytime I disconnect battery cables I remove the grounded one FIRST, was taught that over 60 years ago.

John T

 

[D beatty]

I have mine hooked to ground cable of battery. The one I have you can remove key that turns it off and on.

 

[newhollandnut]

I wired one the combine on the positive side and it would still run down. Dealers mechanic called me one day and told me it needed to be switched. He explained to me why but I can't remember it for the life of me. It was a long time ago but I've been putting them on the negative cable ever since and have had zero issues

 

[MSD]

The one I am going to use is about a ft. from the battery and the battery is in front of the tractor away from the starter.