M charging Trouble Shooting

[ErnieD]

First off I am a little outta my league with a Farmall. SIL has a 6V positive ground M generator with a cut out relay on the generator and 4 pos switch on the dash. A lot of the wiring was butchered
and or missing. I replaced the abandoned wires and verified wiring with online schematic. I am not seeing field voltage (to ground) at either low or high on the dash switch. Gen brushes appear in good
shape.

Tomorrow I was going to check the field resistors on the dash switch and begin John T troubleshooting guide.

Anyone recommend a service manual?

 

[John T]

I am not seeing field voltage (to ground) at either low or high on the dash switch.

Actually (On Class A charging systems) the gennys FLD post needs to be connected to frame ground NOT A VOLTAGE SOURCE in order to charge. The LHBD Light Switch Low High Charge Control system applies a dead ground to gennys FLD post in HIGH charge but a few ohms resistive ground on LOW charge. Often the LHDB switch has a bad ground is the cause of no charge or the wires open from FLD on genny up to the light switch..

At full RPM if you temporarily use a jumper to dead ground the gennys FLD post and that makes her charge, the genny itself is okay but the light switch may have a bad ground. If she fails to charge even with FLD dead grounded and the cutout relay by pass jumped around, the genny may be the problem if all else is correct

https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=ttalk&th=2060825

John T
John Ts Troubleshooting

 

[ErnieD]

Thank you for the clarification. Will report back.