Farmall H wiring question

mrf-engines · Feb 25, 2013

Hello all, got a quick wiring question. I have an original 6 volt system with cutout, and a 4 position switch. Is it possible to bypass the field resistor on the switch for the charging system? I want to see if I have problems with the switch or the generator. Thank you.

Theman · Feb 25, 2013

You are correct. You can ground the field terminal directly and elinimate the cut-out. If the generator starts charging, the contacts in the cut-out may be bad.

John T · Feb 25, 2013

Sure, the Field terminal needs a ground to conduct current to create the electromagnetic field and its not particualr if you or the LHDB switch or a VR provides it....If she charges with FLD grounded but NOT otherwise, the LHDB is bad or not well grounded (typical) or wires open from FLD on genny up to LHBD or VR...

See my Troubleshooting Procedure

John T
John Ts Troubleshooting

Janicholson · Feb 25, 2013

With respect, If the field is grounded, and the generator is actually good, the cutout can still be bad, and no charging can still happen. To test for a bad cutout, it is necessary to jump across the BAT and GEN terminals of the cutout when the field is grounded, and the engine running 3/4 throttle. If it sparks and charges with those jumped, then suspect the cutout. Jim

John T · Feb 25, 2013

If grounding the Field makes her charge, that eliminates the LHDB switch or its not being grounded (often the problem) or the wire from FLD on Genny to the LHDB switch BUT NOT THE CUTOUT RELAY, thats a whole other issue...A MORE COMMON PROBLEM IS THEM STICKING CLOSED versus not latching in. Note a Cutout Relay or a VR needs its own good ground also to function.

John T

mrf-engines · Feb 25, 2013

Thanks for the help. I bypassed the switch and it started showing a charge on the multimeter. When I pulled the cover to check the contacts, I noticed another resistor that was not hooked up inside the cover in the cutout (there is a terminal to hook to it on the outside of the cover). What was this resistor for? Thank you;

John T · Feb 25, 2013

May be the F Terminal Field resistor for connection to the gennys FLD post to provide it a resistive (low charge) ground path on tractors having no lights thus no LHDB light switch.

Thanks Bob M who helped me with that in the past!!!

John T

Farmall H wiring question

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