volt regulator 12v, 2 brush

[Ericp351]

Hi all. I have a 12volt, neg ground MF-35 tractor. Had a Delco 3 brush Generator. Ordered a new Volt Regulator and Generator. Gen now is a 2 brush Lucas and doesn't work with the regulator. Can somebody recommend a volt regulator for this retro-fit? Were the starter generators on older mowers 2 or 3 brush generators?

 

[Janicholson]

Some Lucas generators are A circuit, and some are B circuit. The regulator must match that factor. the 2 brush-3 brush makes little difference. An A circuit uses a field that is supplied with voltage from the armature terminal, (or third brush), and is regulated by grounding the field terminal through the regulator (which must have a good ground from its body to the tractor).
A B circuit has a field that is grounded inside the generator, and is given voltage from the regulator. Very different designs. If the regulator was sent as a match to the generator, it may be OK but needing a good ground. If mismatched, it will never work.
With all wires off the generator, and either one of the brushes lifted off the commutator with an insulator (like a plastic knife blade) the A type will have continuity between the two terminals, and nothing to ground. A B generator will not, but the F terminal will show a connection to ground. (just a few ohms). Jim

 

[Ericp351]

THanks for reply. I am 80% sure is Type A as each brush only has 1 wire, 1 to Gen terminal, one grounded- none to Field. Tried Motor test. Got armature to LOck down and wobble, but not turn. Field to ground and Gen terminal to case ea has a few ohms- not open. Bought Volt regulator as a OEM replacement, then generator from other vender. No output. Did polorize. Getting colder and frustrated!

 

[Janicholson]

The none to field statement you made is an indication of a B generator. An A type would have the internal field connected to the Armature (non grounded) brush. a B generator would show connection to ground all the time. If either brush is lifted from contact with the armature, the B generator will still be connected to ground and show connection with a few ohms, to the F terminal to ground. The A type will still show connection (ohms) between the two terminals (a few ohms. Jim

 

[Ericp351]

Thanks again-Bingo <?>. The field is wired in series, first pole at F, then in series to pole 2, pole 2 to case/ground. Assuming that is B it sounds like I need a B regulator and maybe a new way to Motor-Test. I ran hot to A and Ground to Case and F. Old Ford cars were B, correct? (I may need a application to order the Volt Reg). Please advise if I am missing something else and Thanks Again!! Eric P.

 

[JMOR]

(quoted from post at 17:13:15 11/11/22) Thanks again-Bingo &lt;?&gt;. The field is wired in series, first pole at F, then in series to pole 2, pole 2 to case/ground. Assuming that is B it sounds like I need a B regulator and maybe a new way to Motor-Test. I ran hot to A and Ground to Case and F. Old Ford cars were B, correct? (I may need a application to order the Volt Reg). Please advise if I am missing something else and Thanks Again!! Eric P.

"I ran hot to A and Ground to Case and F." fine for "A"-type, but need "hot to A and F and Ground to Case" for "B"-type

 

[Janicholson]

This should work, or one like it. Jim
One source of a Lucas B regulator

 

[Ericp351]

Thank you again! Was about to order a v reg for a '58 Ford car, but will go with this , affordable Lucas. Last questions (fingers crossed) I assume wire as follows: B to old load and old bat wires. E = earth, short jumper to mount screw. D = to armature spade (British = Dynamo?) F= Field. W/L= not sure, warning light?? Leave open??? Tested B style motor test and Lucas gen is ok, Hope to get this v reg before snow in west Pa.

 

[Janicholson]

The WL is to a indicator. I would use it, but not needed. Jim