I think Im in Bobs camp with what that resistor is, looks like the Field resistor thats used on the back of 4 position LHBD light switches THAT ARE USED WHEN THERES ONLY A CUT OUT ON THE GENERATOR. (3 position switches are for Voltage regulator systtems, see Jims good info) And I agree with him if its open she wont charge in Low charge but still can if all else is right in High charge. Some ammeters use an external shunt and if so and if its open YES that can affect charging BUT ARE YOU SURE THATS A PART OF THE AMMETER???? (again Im thinkin like Bob)
Jim has given you good info on the difference in 3 position switches (used with Voltage regulators) versus 4 position LHBD used with Cutout Relays.
I THOUGHT YOU HAD ALREADY DETERMINED THE GENNY WAS BAD FROM MY TROUBLESHOOTING PROCEDURE????
Heres a part of my Troubleshooting procedure to see if non charging is a genny or a VR problem.
TO DETERMINE IF ITS A GEN OR VR OR CUTOUT RELAY PROBLEM
5. a) VOLTAGE REGULATOR SYSTEM: With the tractor running, temporarily ground the Gens Field post to case. If she charges then but NOT otherwise, the VR may be bad, or a wires missing from VR"s Field post to the Field terminal on the VR, or the VR isn’t well grounded.
b) IF IT’S A CUTOUT RELAY SYSTEM and she charges only if you dead ground the Field but NOT otherwise, its either a bad switch or the switch isn’t well grounded or else the wires bad or open from the Gens Field post up to the switch. INSURE THAT GOOD SWITCH GROUND AND WIRING
6. If she still don’t charge, leave the Field grounded and jump a wire across from the VR or Cutout Relays BAT terminal over to its GEN terminal (jump by passes the cutout relay) and see if she charges. If then but not otherwise, a VR"s cutout relay isn’t working correct (maybe points burned/carboned) or a Cutout Relays NOT working or not wired correct.
7. With the 2 steps above, you have basically by passed the VR or Cutout relays functions, so if she still don’t charge, you"re left with a bad battery or wiring or the Gen itself.
8. MOTOR TEST. You can Motor test the Gen. If its grounded and you remove the belt and apply hot battery voltage direct to its ARM Post and have the Field Post dead grounded to frame, it should motor n run well (Armature n Brushes and Commutator likely okay). Then, if you next remove the Fields ground and it speeds up some, the Fields probably good. If it passes both those tests, it should charge, and if not, it may be a wiring or battery or grounding problem. The hot battery voltage may be taken off the VR"s BAT terminal or the starter post or the battery itself for this test.
You should already have this but heres my complete troubleshooting procedure. You need to determine what you have (3 or 4 position switch and VR or cutout relay) then work through my procedure then post abck your findings and questions so we can help
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