Farmall c charging

BigBob706

Member
Just bought a brand new 6 volt battery, put a switch on to kill all power to battery. Worked one day and now wont charge. My light switch keeps getting hot if the battery is not disconnected, hence the kill switch. Im lost now!
 
Most Farmall C tractors came with a 3 position light switch: Off-O, Dim=D, Bright=B.
Early C might have 4 position: L=low charge, H=High Charge, D=Dim, B=Bright.
I am including a diagram from Bob M (diagram 2 or 3)
There is also a trouble shooting process on the page.
Either the cutout relay points are stuck together (either system has them, the regulator has cutout inside), or there is a short in the light switch.
If three position, the light switch is really not in the charging circuit. If it was shorted, or if the lights are shorted and the switch is on D or B, it can get hot. There is a resistor for D lights that gets hot when on D to cause the lights to be dim. It is in series with the lights and gets way hot, but is not intended to make the switch knob hot.
If a 4 position switch, it is connected to the charging system. The internal components of the switch are not electrically connected, the shaft od the switch rotates 2 different internal switches. One set of contacts controls the lights Dim and Bright. The other set controls charging, Low charge through a resistor to ground (in the switch to the switch body and from that to the switch box and from there to the steering post and thus chassis ground, High charge is direct to ground as before with no resistor. The grounding is used to control the field strength in the generator. The field gets its voltage from inside the generator (third brush or from the armature brush) and is grounded by the light Sw.
The 3 position field circuit is controlled by the regulator, and is not connected to the light switch for control. The L terminal (if it has one) is connected to the Light switch to power the lights, it is an generator output wire not a generator control wire.
I hope this helps. Jim
BobM diagrams
 

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