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Farmall A 3 or 4 pole light switch

H

hayrake25

Member
Hello. I have a 1945 Farmall A that has the cut-out relay on the generator. Which switch do I use, the 3 or 4 pole? Thanks
 
With the relay the 4 position switch would be your choice. The relay doesn't regulate the charge. The 3-position switch is strictly a light switch, off, dim and bright, intended ofr use with a regulator that will determine your charge rate. The two lower positions on the 4-position switch manually regulate the charge rate. Low is the only low charge rate. Hi is charge with no lites. The switch keeps the high charge rate on any time the lights are on in either the dim or bright positions. In all but the low charge position, the current runs directly to ground through the body of the switch. In Low it runs through a resistor before going to ground.
 

4 position (EARLY STYLE with Resistor Strip) is used. The positions are as follows: (L)ow - (H)igh - (D)im - (B)right

The 1st two positions are for the generator charging as it does not have a voltage regulator and the switch acts as one.

The 3rd and 4th positions are for the lights and are self explanitory. They automatically run in the High Charge position.

Make sure the resistor strip on the switch is in good condition, and that a proper fuse is installed. I use a 30 amp glass fuse either in a fuse holder, or on the back of the switch depending if it has a place for one.
 
If you are not concerned about being exactly correct, you will get much better battery life if you will replace the cutout relay with a voltage regulator. You can get one that mounts on the generator like the cutout and looks the same to the casual observer. In that case, you can use either the 3 or 4 position switch. With the regulator, the first two positions on the 4 position switch will just be off. It takes some rewiring to install the regulator, but it's not that difficult and over the long haul you will save the cost of the regulator by better battery life.
 
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