Farmall Bn Mag wiring

I just bought a parts A and it had a mag with a generator that charged,weird thing is that it had a jumper from (F) on the gen to (F) on the cutout plus the wire leaving (F) to the switch.It charged,but when I put it on my BN without the jumper it didn't so I put it back and it charges.i don't see a jumper wire in any diagrams?is this odd or wrong?I have cutouts on both.

Im not surprised it charged, the F on the Cutout consisted of a resistor to frame ground and if the gennys F was also wired to a LHDB light switch, that placed yet another resistor (if in Low) to frame ground in paralell for an even higher charge rate (less net resistance if 2 in paralell). If the LHDB was in High Charge then the field was essentially dead grounded for the highest charge rate possible.

The F on a cutout relay is for a tractor with no LHDB light switch and lights so the genny can still charge cuz the Field has a resistive ground. If it has the LHDB switch the gennys field wires to it so it gets a resistive ground for low charge and a dead ground for high charge.

I would only use one device for charge control so if it has a LHDB switch Id use it and NOT the relays F terminal.

If it has a mag that generates its own power with no connection to or reliance on any battery or charging system.

John T

Thanks for the good info!I took off the F to F jumper wire but I didn't see it charge.It charges all the time and higher with more throttle with the jumper.Does the cutout not charge constantly when wired correct?

I run all mine with cut-outs with the field to the field then wire from the field to the lite sw have been that way for yrs no problems set the third brush for charge amount. Most are mags so you only need couple amps on reg charge get around 6 or so amps on hi-charge. It will be trouble free. The gens # is either a 1101423 or 1101355 original Delco Remy and they have the third brush adjustable. Tractor get lots of miles on rides use around the acreage and battslast 7-8 or more yrs.

Thats not the way mine work with the field connected to the cut-out the third brush is adjusted for normal charge and get around 6-8 amps on hi-charge and they have been that way for many yrs so what is supposed to happen on the long run i have serviced sever Bs over the yrs wired that way also and they work fine. So your Bs are wired the way you say.

Thanks Gene,I will try it one way on my C and the other on my BN.

LET ME TRY AND SUM THIS UP:

1) IFFFFFFF it had a Cutout Relay with the third F Terminal, and the Gennys FLD post is connected to it (and nowhere else) and the relay is good and grounded properly YES IT WILL CHARGE ALL THE TIME DEPENDING UPON RPM AND THE STATE OF THE BATTERY AND GENERATOR and the ohms value of the relays Field resistor.

2) IFFFFFFFFFFF it has a cutout relay and the LHDB light switch and the Gennys FLD post is wired to the light switch ONLY (and nowhere else)which is good and properly grounded IT WILL CHARGE AT THE LOW OR HIGH RATE subject to where switch is set and RPM and state of battery and genny.

3) IFFFFFFFFF it has a cutout relay (with F terminal) and LHDB switch and the Gennys FLD post is effectively connected to BOTH, YES IT WILL CHARGE ALL THE TIME subject to RPM and state of battery and genny and the combined net paralell resistance of BOTH the cutout relays Field resistor and the LHDB field resistor IF IN LOW CHARGE but charges at max charge if IN HIGH CHARGE positiion because then the Gennys FLD is dead grounded.

4) If it has the cutout relay with the F terminal and ONLY an On/Off light switch (NOT the LHDB for charge control) and the gennys FLD is wired to F on the relay yes it will charge all the time subject to RPM and ohms value and state of battery and genny

HOPE THIS HELPS

The Gennys FLD post requires a ground (resistive for low charge, direct to ground for high charge) to charge and it can get it via a relay with the F terminal or using an LHDB switch for the ground source.....

If it charges fine with the gennys FLD grounded but NOT otherwise, the LHDB is bad or not well grounded or the relay (with F terminal) is bad or not well grounded.

Got it?????? Hope this helps

John T

Yes makes perfect sense,Thanks for the time!

All you fellows with electronic questions on Cubs, A's, B's, etc. are dealing with a genius who is named Gene Bender! If he says it will work or not work the way he describes it you can take that advice to the bank.

I am NOT being sarcastic here....speaking from experience when I have had those problems.

Gene Bender is to small Farmalls like Hugh MacKay was to plows.
LA in WI

I agree, on high charge with an LHDB light switch, the gennys FLD post is dead grounded and thats true REGARDLESS if FLD is also wired to a cutout relay or not, a short is a short, so neither the cutout relays field resistor or the light switches field resistor come into play (they are both by passed to frame ground). HOWEVER on Low charge theres a resistor in the field to ground in the LHDB switch and theres also a resistor to ground in the cutout relay SO IN LOW CHARGE SHES GONNA CHARGE AT A LOWER RATE due to lower field current.....

As I posted Im NOT surprised she works that way, as long as the gennys Field gets a ground EITHER OR BOTH using an LHDB switch and/or the curout relay, she will work and still charge more when the field is dead grounded via the LHDB when in HIGH charge

I AGREE she works with the gennys FLD post to both or either a cutout relay (with the F terminal) and/or a LHDB switch.....

The location of any third adjustable brush also affects charge rate as it reduces (if further away) charge or increases (if closer) charge as that affets the field current.....

Hope this helps

Very fun sparky chattin with yall

John T

YOURE WELCOME, glad to be of help

John T