The Ford Barn

Pdgx · 04-17-2022, 11:10 AM

Can anyone tell me what 12v voltage regulator is compatible with a ‘38 vintage, Ford R3 generator ? It’s a 3-brush unit with armature and field leads. Can any 12v Ford regulator (F-A-B) be used ?

Also, this is only needed for charging when using the lights, as the vehicle is crank start only, and mag fired.

I want to leave the generator installed, even though it will not have a battery in the vehicle most of the time. So would like your knowledge on how it should be switched/grounded out to prevent from toasting it, when a battery is not installed.

(It is gear driven, so no, it can’t just have a drive belt loosened)

Would appreciate your input to the questions. Thx.

19Fordy · 04-17-2022, 12:47 PM

Will any of this info help?
https://www.google.com/search?q=1938...hrome&ie=UTF-8

Brian · 04-17-2022, 02:54 PM

3 brush generator only uses a cut-out, mounted atop said generator. Use a 12 volt cut-out. There are two leads coming out of the generator; one is earthed to the cut out mounting screw, the other is attached to the cut out. Simply ground that lead too if you don't wish the generator to charge....
I'd also move the third brush all the way up to reduce charging with the output lead grounded.

Pdgx · 04-17-2022, 02:58 PM

So, ground the field wire, with armature wire going to the cutout ?
Then still ground the armature with no battery ?

Brian · 04-17-2022, 03:52 PM

Yes

Pdgx · 04-17-2022, 05:57 PM

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Thank you !

rotorwrench · 04-18-2022, 08:00 AM

A 3-brush generator is very limited in usable field strength regardless of the system voltage. If a person needs more than 20-amps due to added modern accessories then it should be converted to a 2-brush system and mated with a fully functional voltage and current limiting regulator of either the old style 3-pole system or modern solid state type.

Most folks opt for some form of alternator but I don't care for most of the single wire set ups since they don't always self excite as well as a 2 or 3-wire set up.

terry · 04-19-2022, 01:46 PM

I do have a 12 v regulator that replaces the cut-out...never used. But, as rotor says if you need a lot of amps this may not be your answer until you rebuild the generator to 12 volt specs. Terry

04-17-2022, 11:10 AM	#1
Pdgx Member Join Date: Sep 2013 Location: Central Florida Posts: 56	Ford R3 Generator / voltage regulator Can anyone tell me what 12v voltage regulator is compatible with a ‘38 vintage, Ford R3 generator ? It’s a 3-brush unit with armature and field leads. Can any 12v Ford regulator (F-A-B) be used ? Also, this is only needed for charging when using the lights, as the vehicle is crank start only, and mag fired. I want to leave the generator installed, even though it will not have a battery in the vehicle most of the time. So would like your knowledge on how it should be switched/grounded out to prevent from toasting it, when a battery is not installed. (It is gear driven, so no, it can’t just have a drive belt loosened) Would appreciate your input to the questions. Thx.

04-17-2022, 12:47 PM	#2
19Fordy Senior Member Join Date: May 2010 Location: Coral Springs FL Posts: 10,950	Re: Ford R3 Generator / voltage regulator Will any of this info help? https://www.google.com/search?q=1938...hrome&ie=UTF-8

04-17-2022, 02:54 PM	#3
Brian Senior Member Join Date: May 2010 Location: Masterton, New Zealand Posts: 3,834	Re: Ford R3 Generator / voltage regulator 3 brush generator only uses a cut-out, mounted atop said generator. Use a 12 volt cut-out. There are two leads coming out of the generator; one is earthed to the cut out mounting screw, the other is attached to the cut out. Simply ground that lead too if you don't wish the generator to charge.... I'd also move the third brush all the way up to reduce charging with the output lead grounded. __________________ Unfortunately, two half wits don't make a whole wit!

04-17-2022, 02:58 PM	#4
Pdgx Member Join Date: Sep 2013 Location: Central Florida Posts: 56	Re: Ford R3 Generator / voltage regulator So, ground the field wire, with armature wire going to the cutout ? Then still ground the armature with no battery ? Last edited by Pdgx; 04-17-2022 at 03:03 PM.

04-17-2022, 03:52 PM	#5
Brian Senior Member Join Date: May 2010 Location: Masterton, New Zealand Posts: 3,834	Re: Ford R3 Generator / voltage regulator Yes __________________ Unfortunately, two half wits don't make a whole wit!

04-17-2022, 05:57 PM	#6
Pdgx Member Join Date: Sep 2013 Location: Central Florida Posts: 56	Re: Ford R3 Generator / voltage regulator Sponsored Links (Register now to hide all advertisements) Thank you !

04-18-2022, 08:00 AM	#7
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: Ford R3 Generator / voltage regulator A 3-brush generator is very limited in usable field strength regardless of the system voltage. If a person needs more than 20-amps due to added modern accessories then it should be converted to a 2-brush system and mated with a fully functional voltage and current limiting regulator of either the old style 3-pole system or modern solid state type. Most folks opt for some form of alternator but I don't care for most of the single wire set ups since they don't always self excite as well as a 2 or 3-wire set up.

04-19-2022, 01:46 PM	#8
terry Senior Member Join Date: May 2010 Posts: 267	Re: Ford R3 Generator / voltage regulator I do have a 12 v regulator that replaces the cut-out...never used. But, as rotor says if you need a lot of amps this may not be your answer until you rebuild the generator to 12 volt specs. Terry