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1937 Cadillac generator

Started by VooDoo, March 11, 2023, 03:29:07 PM

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VooDoo

So, according to my mechanic, my generator is not charging my battery correctly. Since I need to replace it, I was wondering if anyone has replaced a generator with a 6 V alternator? I've been reading, and it seems like the alternator would provide more power, especially at night, driving with the lights on. I plan on driving my Caddy for wedding events and such so I need to make sure that everything is top notch. Anyone have any experience with this and or recommendations? I can always buy a rebuilt generator but I kind of figured if the alternator is going to provide me with better charging, etc. then why not go that route? Thanks guys I really appreciate it. I'll post this in the general discussion section just in case more individuals are viewing that but moderators, Please feel free to remove it if need be. I need to get this sorted as quickly as possible.
Andy Fulenwider
1937 75 Series Convertible
1947 62 Series Custom Project

bcroe

I would first check the brushes, which was always
the failure in my generator days.  If the Gen has
trouble maintaining voltage for your night driving,
lights diming, an alternator should do better. 
Taking care of clean, aligned, and probably
upgraded headlights is likely more important.  A
6V alt is not as efficient, as the output is
already down a couple volts from the diode bridge,
less of an issue at 12V.  More power and better
system voltage regulation comes at 12V, if needed. 
Bruce Roe

Ohjai

How is the operation of your Voltage Regulator?  It may not be adjusted properly.
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VooDoo

Quote from: Ohjai on March 11, 2023, 06:31:54 PMHow is the operation of your Voltage Regulator?  It may not be adjusted properly.


Seems to be reading correctly.. Mechanic says even when reving never got over around 6.4 V
Andy Fulenwider
1937 75 Series Convertible
1947 62 Series Custom Project

Dave Shepherd

Not true, output can be 7.5 volts with no issues.

VooDoo

Quote from: Dave Shepherd on March 11, 2023, 06:46:50 PMNot true, output can be 7.5 volts with no issues.
What I'm saying I guess is the output never got over 6 V so that's why he was saying he didn't think it was charging correctly
Andy Fulenwider
1937 75 Series Convertible
1947 62 Series Custom Project

VooDoo

Quote from: Dave Shepherd on March 11, 2023, 06:46:50 PMNot true, output can be 7.5 volts with no issues.
To be clear, the reading across the generator wasn't higher than 6 V
Andy Fulenwider
1937 75 Series Convertible
1947 62 Series Custom Project

VooDoo

Quote from: Ohjai on March 11, 2023, 06:31:54 PMHow is the operation of your Voltage Regulator?  It may not be adjusted properly.
Sorry I was referring to the gauge inside the car. How do you adjust and or check the actual voltage regulator? And what should it be?
Andy Fulenwider
1937 75 Series Convertible
1947 62 Series Custom Project

bcroe

Quote from: VooDooTo be clear, the reading across the generator wasn't higher than 6 V

With some revs and light load, you should see at
least 7V for charging.  Bruce Roe

VooDoo

Quote from: bcroe on March 11, 2023, 11:06:03 PMWith some revs and light load, you should see at
least 7V for charging.  Bruce Roe
that sounds like generator is bad for sure? If so, got any thoughts on switching to an 6v alternator vs generator?
Andy Fulenwider
1937 75 Series Convertible
1947 62 Series Custom Project

bcroe

Quote from: VooDoothat sounds like generator is bad for sure? If so, got any thoughts on switching to an 6v alternator vs generator?

My opinion, if the brushes are OK and the generator
is putting out current, the problem is the voltage
regulator.  If it cannot deliver enough current to
get to 7V, bad generator.  A 6V alternator works;
if used with an internal regulator, should also
eliminate a source of radio interference (leaving
about 6 others to fix).  And considerably extend
the service interval.  But pricey compared to 12V.
good luck, Bruce Roe

fishnjim

Has the generator/VR been polarized recently?   It won't charge if it's not polarized right.
Start with a fresh battery when chasing these things down.   If it's not been working for a while/sitting, battery wet cells become polarized/sulfated and that's why the output is down - dim lights.  Full charge would be 6.3-4 VDC.  So its not fully charged at 6.0.
Also connections are key.  Anodes/cables - No corrosion zone.   
If mech's got an output tester, then he should be able to tell, but may not be that familiar with gen/VR systems.  They can test the generator at a auto electric shop and tell you what condition it's condition is in.
I'd replace the VR too, as that's an easy one.  Contacts are subject to corrosion.
Plus generator has to turn a certain speed to get any output.  Not much going on charge wise at 4-600 rpm idle. >700 rpms ~ bottom of the output curve.

I have no comment on a 6V alternator.  That's "backward migration of technology". Seems a waste to me.  Either make what you got work good or go 12V. 
A lot of 6V issues are age of wire and other resistance inducing issues related.  They can work fairly well it maintained properly.  They won't compete with the LEDs of today in terms of output, no matter what voltage. 

Poncholover

I have heard of 8 volt generators being an option, though I know little of them.
Anyone?
Flattie Caddy

VooDoo

Quote from: fishnjim on March 12, 2023, 02:26:39 PMHas the generator/VR been polarized recently?   It won't charge if it's not polarized right.
Start with a fresh battery when chasing these things down.   If it's not been working for a while/sitting, battery wet cells become polarized/sulfated and that's why the output is down - dim lights.  Full charge would be 6.3-4 VDC.  So its not fully charged at 6.0.
Also connections are key.  Anodes/cables - No corrosion zone.   
If mech's got an output tester, then he should be able to tell, but may not be that familiar with gen/VR systems.  They can test the generator at a auto electric shop and tell you what condition it's condition is in.
I'd replace the VR too, as that's an easy one.  Contacts are subject to corrosion.
Plus generator has to turn a certain speed to get any output.  Not much going on charge wise at 4-600 rpm idle. >700 rpms ~ bottom of the output curve.

I have no comment on a 6V alternator.  That's "backward migration of technology". Seems a waste to me.  Either make what you got work good or go 12V. 
A lot of 6V issues are age of wire and other resistance inducing issues related.  They can work fairly well it maintained properly.  They won't compete with the LEDs of today in terms of output, no matter what voltage. 
I've never polarized the generator. Is there a specific process for that that you can refer me to?
Andy Fulenwider
1937 75 Series Convertible
1947 62 Series Custom Project

VooDoo

So I fault instructions I found online about polarizing the generator. Took a jumper cable put it to the air terminal and then touched the negative side of the battery, and that was supposedly all that was needed to polarize it. Hopped in the car, turn the key on, saw the amp meter drop a little, started the car up at Hubbard just below the middle, sat there and revved the vehicle for a little while and the amp meter never moved to the charge side. While running, I turned on the lights and saw the amp meter drop so I believe the amp meter is functioning correctly. What would be my next step?
Andy Fulenwider
1937 75 Series Convertible
1947 62 Series Custom Project