Where is my electrical short?

[farmalluver]

I have an issue with my Farmall C (6 volt) shorting out when I engage the starting motor. Last week I cleaned the battery terminals and the ground location on the torque tube. The starter motor worked twice but now shorts again when I pull the starting rod. If I tap on the positive terminal after it shorts, the ammeter will show discharge again the way it is supposed to. I don't have any issues with starting with a hand crank as long as the ammeter is discharging when I pull the starter button out. The lights work and the ammeter shows charge when the engine is running. I just put in a new rebuilt starter motor and it shorts right away. Where is my short?

 

[Smarten_up]

Are you sure its a short circuit? On my C sometimes the battery positive terminal looses proper connection and I have to wiggle it to get it to work.Thats even after cleaning the battery posts and connectors. And I've also experienced a bad connection at the starter motor/contactor. If you really had a short circuit I'd expect to see smoke coming from some wire somewhere melting.

 

[Janicholson]

With respect, a short circuit is one that causes fuses to blow, or things to get hot and start fires. They are like cutting an extension cord in half with a wire cutter when it is plugged in! You have an open an open is when a circuit is not complete. The reason could be a broken wire or corrosion in a wire, or a faulty terminal, or a disconnected component. Because nothing works when it won't start, it is likely in the big battery cables, or the wire from the starter switch on the starter that goes to the electrical box. (less likely) A internally failed connection inside a battery can also happen. A automotive test light will find the issue. Connect the clip of the test light to a shiny spot on the grounded battery terminal. Check by touching the opposite terminal and continuing to follow the fat wire until you find a point at which it does not light. There is the problem. Jim

 

[Charlie M]

Do you have a saddle switch on the starter - those things can junk up easily and not make good contact.

 

[Rick Remmert]

I would second that. Yes, the Super C's do have a saddle switch on top of the starter. I got mine back from the starter shop after having it switched over to 12 volt. They put a brand new switch on the starter and it was missing one of the brown paper insulation pads. They sent me a new and I was good to go. They are very cheaply made.

 

[rustred]

what is shorting when pulling the starter rod??? if nothing is happening how can it be shorting?? you have a poor connection inside the starter switch. take it off and clean the contacts inside and turn post around inside. it is not a short.

 

[farmalluver]

I think testing the system from the battery out is a good suggestion. I will give it a try. I know it is definitely not associate with the saddle switch since had two different switches, one being brand new. One question I might have is why would my tractor start and lights still work if I have a bad cable--either the ground or the hot cable? I am also going to test the battery, maybe it got froze this winter and I have a bad cell or something. Thanks for the input.

 

[Smarten_up]

Power to the coil/distributor goes through a different wire from the battery positive. Whereas the big wire goes directly from battery positive to the starter pull rod switch. As long as the key is on the coil will have power and the engine will start by way of the hand crank. You have a bad or very poor cable connection somewhere between the battery and the starter switch. Just maybe the battery is too weak to crank the starter, bad cell?

 

[504]

Did you polish the post on the starter, that the saddle switch hits when you pull the rod?(under the switch)

 

[Rodney51Cub]

(quoted from post at 15:04:02 04/15/23) If I tap on the positive terminal

If I am reading this correctly you are tapping the positive terminal at the battery, which on a 6 volt system should be ground. I would change the ground cable it may be internally corroded. You could check it by using a set of jumper cables and hook from the battery to a ground spot on the tractor and see if this changes anything.

 

[used red MN]

It sounds to me like you have an intermittently bad battery connection at one of the post terminals or you have a battery cable losing conductivity, which means for some reason it is not carry power through it like it should. Your ammeter is simply not showing a discharge because no actual power is moving through it because of the bad connection. A couple things to check, are the inside surfaces of the battery terminals post clamps clean inside. Sometimes they get a black hard residue on the inside. This can actually cause them to not make a proper connection. A brush style cleaner may not properly clean this type of residue. You need to have a blade type terminal cleaner as shown in the link or use a utility knife to scrape them down to shiny bare lead. One or more of the cables may have bad continuity as mentioned above. This may be because the installation looks fine but underneath it the crimp is loose or the cable itself is deteriorating. This can be checked with a test light. Reply back if you need more instructions for that.
Terminal cleaner

 

[BarnyardEngineering]

If you see a spark at one or the other battery post when you hit the starter, that is NOT a "short."

That is an ARC. You have a bad battery connection. A spark jumps across the bad connection, and creates soot, which then insulates the connection completely.

Get a battery terminal cleaning tool. The kind with the wire brush and the cup with all the fingers. Use it on the battery post and cable terminal.

 

[John T]

Sounds more like its a bad/resistive/arcing connection, battery cable, or a faulty starter switch NOT A
SHORT....

At anyplace you saw sparks or there's evidence of heating at any connection such as battery posts or
ground connections or starters, starter switches or solenoids etc etc REMOVE CLEAN N WIRE BRUSH and re
attach each n every connection and terminal etc. The battery cable to frame ground connections can go bad
and the ground cables themselves.....

Those mechanical push down saddle mount starter switches (ifff thats what you have ??) can develop pits
and carbon and she wont crank. Check that as well as where the big cable attaches to it

John T

 

[John T]

OOPS posted in wrong place I meant up top MY BAD sorry

John T

 

[gene bender]

if you had a short it would get hot and burn and smoke you have a bad conection thats open and thats why the starter doesent work mite need new cables get the starter and saddle sw checked the stud going to the fields can go bad take the starter to a starter shop mite just need a new stud soldered.

 

[farmalluver]

Problem solved. Thanks all for your input. My bad for using the wrong term short instead of arc. I did use my test light but found I didn't have any dead spots. I tried a different battery to ground cable and everything worked as it should. My old cable was a large #2 gauge wire and it looked good but it must have had some cracks in it because my lights would still work just couldn't handle the amps when the starting motor was engaged.

 

[John T]

Congratulations, thanks for the feedback

John T