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Old 12-15-2025, 11:14 AM   #21
Bazooka Joe
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Default Re: What type of alternator is this on my 40 Ford.

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Joe,
I'd never witnessed an alternator that did not have an identification number stamped into the case. With that number, a decent counter person at NAPA can quickly look it up and tell you the EXACY (original) application and the modern equivalent. Now, to find a decent counter person...that may be tough.
Yes, probably will start with this place also, as a backup to Napa or any other auto parts store, as the 10Si shows different amp. ratings, just looking for the same one I have. Does say 10A on the casing also.

https://alternatorparts.com/how-to-i...lternator.html

Thankx for the help..
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Old 12-15-2025, 11:29 AM   #22
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Default Re: What type of alternator is this on my 40 Ford.

Look again, I doubt it is 10 amp, smallest I've seen is 40 amp
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Old 12-15-2025, 12:54 PM   #23
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Default Re: What type of alternator is this on my 40 Ford.

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Look again, I doubt it is 10 amp, smallest I've seen is 40 amp
Probably a casting number ( looks like it says 10 A to these ole eyes ) or series number? of some sort, having nothing to do with amprege rating..
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Old 12-15-2025, 01:56 PM   #24
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Default Re: What type of alternator is this on my 40 Ford.

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Probably a casting number ( looks like it says 10 A to these ole eyes ) or series number? of some sort, having nothing to do with amprege rating..
That's a casting number of the bracket. On the BODY of the alternator there is a number stamped INTO (not raised) it.
As a general rule (there are of course exceptions) raised numbers are nearly always casting numbers. Recessed numbers are nearly always identification numbers.
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Old 12-15-2025, 02:50 PM   #25
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Default Re: What type of alternator is this on my 40 Ford.

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That's a casting number of the bracket. On the BODY of the alternator there is a number stamped INTO (not raised) it.
As a general rule (there are of course exceptions) raised numbers are nearly always casting numbers. Recessed numbers are nearly always identification numbers.
That’s great info, did not know that raised digits where casting, and recessed digits where ID numbers, generally speaking. That has been logged and noted. Heck I’m still learning at 70+ years old…

Thankx

Joe
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Old 12-15-2025, 04:36 PM   #26
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Default Re: What type of alternator is this on my 40 Ford.

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Probably a casting number ( looks like it says 10 A to these ole eyes ) or series number? of some sort, having nothing to do with amprege rating..
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Old 12-15-2025, 06:01 PM   #27
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Default Re: What type of alternator is this on my 40 Ford.

[QUOTE=Gene1949;2427672]Gee wizz guys, give the man a break. Nobody really cares who is the better “purist”. He asked a simple question.. Anyways,
I would wire it correctly according to GM. The 1 wire does work but you will be a lot happier with the idoit light and sensing wire setup. Lot better performance at low RPMs like our flatties run. Also install the smallest pully you can find. That also helps at low rpms.

I'm with Gene, post 18. BFD if it's not 'purist'. And, I would wire it, like Gene said, per GM. Screw the one wire deal. Only the crowd with sanitary/sterile engine bays worship the one-wire nonsense. As for a replacement, any counterman should be able to solve that. If nothing else, just say 73 Chevy Impala 350... or whatever. If I were close, I'd be happy to assist. I'm sure my stash has a few working alternators of that variety. (And, stash has enough parts to fix any possible problem that your alt has.) Just sayin.....
(just for the record, and obviously OT, the last few conversions I've worked on, I used a FORD alternator, no matter what the engine was. I think the Ford alternator has a slightly cleaner-looking case. Something about a GM alternator, under a Ford hood, just doesn't look right to me. I have especially noticed this on Model A bangers. And yes, I've used the Ford alternator on top of a Chevy engine, in a Ford.) (Currently working on a 41. Torn between using a generator, or alternator.... on flathead engine.)
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Old 12-15-2025, 06:07 PM   #28
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Default Re: What type of alternator is this on my 40 Ford.

What voltage output do you get if you push a small screwdriver in the D shaped hole as shown in the # four picture (11 o'clock position). By using the small screwdriver to ground the regulator tab you bypass the regulator and are checking the max output of the alternator.
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Old 12-15-2025, 06:33 PM   #29
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Default Re: What type of alternator is this on my 40 Ford.

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What voltage output do you get if you push a small screwdriver in the D shaped hole as shown in the # four picture (11 o'clock position). By using the small screwdriver to ground the regulator tab you bypass the regulator and are checking the max output of the alternator.
Never tried that, not sure how to do it anyway, I do see the slot you’re talking about. I’m thinking I’ll just keep the world economy moving forward and purchase a new one and be done with it. I believe this alternator itself is pretty old.

Off to the next problem…..

Thank You for your input…
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Old 12-15-2025, 07:26 PM   #30
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Default Re: What type of alternator is this on my 40 Ford.

Joe, to test your alternator using a DC voltmeter or multimeter connected to the main alternator battery terminal. No good testing at idle, you need some revs up say around 1500 RPM and you should read at least 13.5 to 14 volts. Do that and report results back to me. Regards, Kevin.
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Old 12-15-2025, 07:43 PM   #31
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Default Re: What type of alternator is this on my 40 Ford.

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Joe, to test your alternator using a DC voltmeter or multimeter connected to the main alternator battery terminal. No good testing at idle, you need some revs up say around 1500 RPM and you should read at least 13.5 to 14 volts. Do that and report results back to me. Regards, Kevin.
OK, but 1st I have to put the alternator back in….OK so put positive lead of meter on batt. terminal on back side of alternator and negative lead of meter to a good ground and get RPM up a bit, correct..

I only checked it at idle and at the battery itself ( battery in the trunk ) , reading 12.20 VDC. With idle and headlights on 12.04 VDC at brand new battery.

Last edited by Bazooka Joe; 12-15-2025 at 09:05 PM.
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Old 12-15-2025, 08:23 PM   #32
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Default Re: What type of alternator is this on my 40 Ford.

[QUOTE=bobH;2427744]
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Originally Posted by Gene1949 View Post
Gee wizz guys, give the man a break. Nobody really cares who is the better “purist”. He asked a simple question.. Anyways,
I would wire it correctly according to GM. The 1 wire does work but you will be a lot happier with the idoit light and sensing wire setup. Lot better performance at low RPMs like our flatties run. Also install the smallest pully you can find. That also helps at low rpms.

I'm with Gene, post 18. BFD if it's not 'purist'. And, I would wire it, like Gene said, per GM. Screw the one wire deal. Only the crowd with sanitary/sterile engine bays worship the one-wire nonsense. As for a replacement, any counterman should be able to solve that. If nothing else, just say 73 Chevy Impala 350... or whatever. If I were close, I'd be happy to assist. I'm sure my stash has a few working alternators of that variety. (And, stash has enough parts to fix any possible problem that your alt has.) Just sayin.....
(just for the record, and obviously OT, the last few conversions I've worked on, I used a FORD alternator, no matter what the engine was. I think the Ford alternator has a slightly cleaner-looking case. Something about a GM alternator, under a Ford hood, just doesn't look right to me. I have especially noticed this on Model A bangers. And yes, I've used the Ford alternator on top of a Chevy engine, in a Ford.) (Currently working on a 41. Torn between using a generator, or alternator.... on flathead engine.)
Thankx for the information…
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Old 12-15-2025, 08:30 PM   #33
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Default Re: What type of alternator is this on my 40 Ford.

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Not debating anything. its a nice car, and the man is asking for help. If thats a problem you should click the back button.
Needed to be said.
Anyways, I ran the chebbie alt for many year until my hearing loss became bad enough I couldn't hear the stereo very well. Replaced the 10si with a Ford Taurus 130 amp.
Pure economics. $6000 for hearing aids OR 1200 dollars for kick ass speakers and an 800 watt amp
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Old 12-16-2025, 09:26 AM   #34
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Default Re: What type of alternator is this on my 40 Ford.

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Originally Posted by koates View Post
Joe, to test your alternator using a DC voltmeter or multimeter connected to the main alternator battery terminal. No good testing at idle, you need some revs up say around 1500 RPM and you should read at least 13.5 to 14 volts. Do that and report results back to me. Regards, Kevin.
Reporting back as ordered……must be my military days kickin in,….After cleaning all terminals at alternator and the two pins, on side of alternator getting 14+ VDC at alternator after getting RPM 1500+. Seems all is set. Rechecked at battery in the truck, similar voltages.

Off to next project, R&R non functional vacuum wiper and going 12 VDC electric wipers.

Thankx for the advice….
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Old 12-16-2025, 09:37 AM   #35
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Default Re: What type of alternator is this on my 40 Ford.

Recommend Newport Wipers for your conversion. JMO
https://newportwipers.com/product/1940-ford/#switches
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Old 12-16-2025, 11:18 AM   #36
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Default Re: What type of alternator is this on my 40 Ford.

back in my day working for the cadillac dealer i rebuilt lots and lots of those alt.the amp number is stamped where the adj. bolt is it will read like 63 A. or 85 A and the other numbers will give you what your looking for hope this helps
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Old 12-16-2025, 11:25 AM   #37
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Default Re: What type of alternator is this on my 40 Ford.

the numbers are on the top of the case that bolts to the front housing right behind the adj. bolt i could see it on the one picture you sent but it was upside down and couldn’t get my pewter to lock in to see it but if you have it working by cleaning the terminal great easy fix
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Old 12-16-2025, 11:37 AM   #38
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Default Re: What type of alternator is this on my 40 Ford.

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Thanks for the support. I was beginning to think I was the odd man out.
Your comment put a smile on my face, keep up the good work.
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Old 12-16-2025, 07:08 PM   #39
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Default Re: What type of alternator is this on my 40 Ford.

I changed my 46 pickup to 12v, but only cause I got a real hungry 12v winch on the back. My young NAPA guy knew exactly which alternator I wanted.
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Old 12-16-2025, 07:49 PM   #40
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Default Re: What type of alternator is this on my 40 Ford.

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back in my day working for the cadillac dealer i rebuilt lots and lots of those alt.the amp number is stamped where the adj. bolt is it will read like 63 A. or 85 A and the other numbers will give you what your looking for hope this helps
I seen a partial number of 61A stamped along with other numbers, so guessing they made them in 61 amps. as well as 63 amps? Anyway I’m all set, Thank You
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