B Re-wire

[matthewh]

Found the battery dead on my B (have not had it long). When I hooked jumper cables, It did not take long to find the insulation burning off the wire going from bat to alternator (Delco). Don"t know yet if wiring ground or alternator problem.

Question - when sizing up the rewire job, I did not find a fuse anywhere. I plan to add a fuse where the lights and ignition branch off. Also planning to add a fuse to the charging circuit, but which end. The battery end would have prevented my current problem, but should there also be a fuse on the alternator end?

 

[PBrowning]

Matthew -- Two solid data sources can be found at the John Deere Model H Restoration Site, one a wiring diagram for the B John Deere, and also another for the H John Deere. See the URL (below) for your B.

And then using the same URL, substitute JD-H in for JD-B because in the H wiring diagrams section, you will find wire sizes that also apply to your tractor -- and perhaps a whole lot more that is similar, but in a different format. (PatB)
Wiring Diagrams, JD B

 

[John T]

Of course, this isnt original, but if you wanna add some over current protection, the main hot battery voltage feed for lights and ignition (if its a coil ignition not a mag) is off the ammeters Load (NOT to battery/starter) terminal (same terminal that wires to the alternators output stud) and I would use a 15 or 20 (depends on load and size of wire used) amp fuze, then wire the lights/ignition switch input terminal downstream of the protective device.... The alternator has its own limiting but if you still wanna protect that, Id use a circuit breaker and size it to the alternators current rating and wire used (like 30 or 40 amps etc) and it would wire at the alternators output where it connects up to the ammeter.

They didnt use fuses originally on a lot of tractors, they depended upon the wire itself to serve as the overcurrent protection sort of like a piece of fusible wire link

John T

 

[johns48jdb]

just a question here. did you wire it up backwards to the tractor. your tractor has a positive ground.

 

[matthewh]

Thanks, that is exactly the way I wired it. I did not start it (It is raining in Georgia - left it in the shop). Lights and power to ignition ok. Alternator seems ok with meter and I will check charging another day. Bad news is I did not find out for sure what went wrong. In any case, I have circuit protection. thanks

 

[matthewh]

Not 6 volt or positive ground anymore. Several things changed from original before I found her. For now, she is in working trim. May restore one day. I did replace a battery cable end today. The new end used a metric fastner. I felt guilty as I am sure that is a violation.

tks

 

[matthewh]

Thanks, big help. In all cases, the charging circuit is separate from the light/ignition circuit all the way back to the generator/volt reg. I am curious as to why. Are you familiar with what is going on here?

thanks again

 

[PBrowning]

I think John T kind of hinted in that direction. The light fuse is meant to protect the (precious) light switch in event of the many dumb things that can happen during operation. But short of a small fire, the other components weren't designed with any protection other than a dead short resulting in a wire burning open! I doubt that such failures were that much of a problem "in the day" -- at least if they were, I didn't hear of them. (PatB)

 

[johns48jdb]

i went over to visit a neighbor who had been raking some hay several days before with a 50 jd. i drove up in the yard and i could see the wiring on it smoking. i janked the cables off of it and looked the boy up and told him about it. now i don't understand how a tractor just sitting there could, after severl days of not being used, nearly catch on fire from the burning cables. i keep threating to put a cut off switch on my b or at least take the battery cable off it it each time i park it and don't. guess i'll wait til it burns and then do it.