Tom Walker
Senior Member
Reading Barnfind08's post on generator wiring, I wanted to bring up something that has been brewing in my mind for a while. My question is....is there any way of varying the charge output of an old Ford equipped with a 3 brush generator with 2 wires coming out of it, other than by adjusting the movable brush?
I have sent my "one wire" generator off to be fixed, it stopped charging. While it was still on the car, I read up on 3 brush generators so I could test it. The "one wire" unit has its output to the cut-out then to the ammeter to provide charging. The "2 wire" unit has the same output wire, with another simply going to ground under the cut-out case.
This second wire is, I believe, the ground for the field coils. On the "one wire" unit, the field coils are grounded inside the casing. In other words, the 2 gennies are exactly the same (in their wiring, at any rate), but one has its field coils grounded outside the case, the other inside.
So if you have a one wire genny, you cant do much about the output other than buy a clever cut-out/regulator box, and manually adjust the movable brush. If you have a 2-wire genny, I believe you can vary the charge by running the field coil ground wire through resistance.
It seems to me that this could provide you with a useful control of genny output, at the cost of a bit of wire, a resistor, and a switch. A two way switch on the dash could send this field coil wire straight to ground (when lights are on) or to ground via resistance (lights off). Play with the movable brush to get the basic output right. I had an old tractor that had a 2 stage charging system, and I think the resistance was provided by a bulb,which lit to remind you that you were on low charge. Now I think I understand a little more about how it worked.
I suppose I go back to my original question...was there ever any switched output variability on the 3 brush, 2 wire generator equipped Fords?
Thanks, Tom.
I have sent my "one wire" generator off to be fixed, it stopped charging. While it was still on the car, I read up on 3 brush generators so I could test it. The "one wire" unit has its output to the cut-out then to the ammeter to provide charging. The "2 wire" unit has the same output wire, with another simply going to ground under the cut-out case.
This second wire is, I believe, the ground for the field coils. On the "one wire" unit, the field coils are grounded inside the casing. In other words, the 2 gennies are exactly the same (in their wiring, at any rate), but one has its field coils grounded outside the case, the other inside.
So if you have a one wire genny, you cant do much about the output other than buy a clever cut-out/regulator box, and manually adjust the movable brush. If you have a 2-wire genny, I believe you can vary the charge by running the field coil ground wire through resistance.
It seems to me that this could provide you with a useful control of genny output, at the cost of a bit of wire, a resistor, and a switch. A two way switch on the dash could send this field coil wire straight to ground (when lights are on) or to ground via resistance (lights off). Play with the movable brush to get the basic output right. I had an old tractor that had a 2 stage charging system, and I think the resistance was provided by a bulb,which lit to remind you that you were on low charge. Now I think I understand a little more about how it worked.
I suppose I go back to my original question...was there ever any switched output variability on the 3 brush, 2 wire generator equipped Fords?
Thanks, Tom.
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