Upgrading 37amp Alternator to a 50amp?
Alternator needs 2 fields on opposite "ends" of the rotor to work, like a circuit needs a complete path. Old ones used 1 field as the power in (blue wire terminal) and the other field brush as the ground (internally grounded to the case, but its still a brush, you can take it out and find its uninsulated from the brush to the case). The newer "isolated field" or "2 field terminal" alternators used the 2nd brush (thats usually hard grounded to the case in the old ones) as a "floating ground" that's isolated from the case, brought back to the electronic voltage regulator via the green wire and grounded through that (a variable ground to regulate the output of the alternator) devices case, bolted to the firewall. Careful, there are 2 slip rings in the winding and possible 3 potential brush locations. There is a vertical and horizontal brush that ride on the 2 slip rings that are on "opposite" sides of the rotor. Dont use the same slip ring (the brush locations opposite each other, they tap the same slip ring!) as a power and a ground or floating ground. It wont work, youll be tapping both off one side (slip ring) of the rotor. I believe the old roundback 1 terminal alternator uses the grounded brush on the flat slip ring that is parallel to the parting lines of the case. The power brush rides on the slip ring that is barrel shaped. When you get a brush set, youll see one is shaped like an "L" (flat slip ring contact) and one is shaped like a "C" (power, barrel shaped slip ring contact). So..if you look at the roundback alternator with the mounting bracket pointing up at 12:00, the power terminal is at 12 and the ground terminal is at 9, 3 is the place for the new isolated field brush (or use 9 if 3 is not tapped) Some even have FLD cast in the brush location, even though there is no brush there.
Alternator needs 2 fields on opposite "ends" of the rotor to work, like a circuit needs a complete path. Old ones used 1 field as the power in (blue wire terminal) and the other field brush as the ground (internally grounded to the case, but its still a brush, you can take it out and find its uninsulated from the brush to the case). The newer "isolated field" or "2 field terminal" alternators used the 2nd brush (thats usually hard grounded to the case in the old ones) as a "floating ground" that's isolated from the case, brought back to the electronic voltage regulator via the green wire and grounded through that (a variable ground to regulate the output of the alternator) devices case, bolted to the firewall. Careful, there are 2 slip rings in the winding and possible 3 potential brush locations. There is a vertical and horizontal brush that ride on the 2 slip rings that are on "opposite" sides of the rotor. Dont use the same slip ring (the brush locations opposite each other, they tap the same slip ring!) as a power and a ground or floating ground. It wont work, youll be tapping both off one side (slip ring) of the rotor. I believe the old roundback 1 terminal alternator uses the grounded brush on the flat slip ring that is parallel to the parting lines of the case. The power brush rides on the slip ring that is barrel shaped. When you get a brush set, youll see one is shaped like an "L" (flat slip ring contact) and one is shaped like a "C" (power, barrel shaped slip ring contact). So..if you look at the roundback alternator with the mounting bracket pointing up at 12:00, the power terminal is at 12 and the ground terminal is at 9, 3 is the place for the new isolated field brush (or use 9 if 3 is not tapped) Some even have FLD cast in the brush location, even though there is no brush there.
