Voltage Regulator sets the Amperage of the Charging System?

[Beemon]

So I was informed by an electrical shop that it's the voltage regulator, and not the internals of the generator, that determines what the amperage of the charging system is. Is this true? This is the same shop that rebuilt my old starter that blew up, admittedly I got desperate for a new armature for the generator before buying a rebuilt Chevy one online that so happened to have the correct sized pulley. If it is true, why don't people just buy the 35 amp voltage regulator vs the 30 amp? The 35 amp voltage regulator is $65 cheaper than the 30 amp voltage regulator.

[SpecialEducation]

Voltage regulator has 3 functions:

 

1.  Voltage regulation (duh?)

2.  Reverse current cut-out. 

3.  Ampere limiter. 

 

The service manual tells how to set/check these functions on the car, but you have to have a 30 amp ammeter to do it.  

[SpecialEducation]

I bought something similar to this for the job, just before switching to an alternator...

https://www.ebay.com/itm/US-DC-100V-10-50-100A-Voltmeter-Ammeter-LED-Dual-Digital-Volt-Amp-Meter-Gauge-/253530841811

[Bloo]

4 hours ago, Beemon said:

So I was informed by an electrical shop that it's the voltage regulator, and not the internals of the generator, that determines what the amperage of the charging system is. Is this true?

 

Yes (well, yes assuming we are talking about post 1940 systems with 3 relays inside the voltage regulator). A generator will charge as hard as it possibly can if asked, and go up in a puff of smoke. There is a limit to how much current any given type of generator can safely generate. The current regulator (inside the voltage regulator assembly) is set to the maximum current the generator can safely take. To get more current capability, you put on a bigger generator, and then set the current regulator to the newer higher limit. If it is a huge change a different regulator might be needed.

 

4 hours ago, Beemon said:

If it is true, why don't people just buy the 35 amp voltage regulator vs the 30 amp? The 35 amp voltage regulator is $65 cheaper than the 30 amp voltage regulator.

 

If you mean brand new regulators, I don't know why people buy any of those. The riveted on covers are proof positive the makers have no idea what they are doing.

 

It has been a long time since I ran into an old regulator that needed more than points cleaning and a setup. I am sure they are out there, after all, breaker points can wear out, but Ebay and the swap meets are full of NORS replacements.

 

 

Edited September 24, 2018 by Bloo (see edit history)

[SpecialEducation]

Most people aren't equipped to measure amp draws that high. Running a 30 amp generator at 35 amps could overheat it to the point that you start melting the solder inside.

Buying a new regulator and assuming it's set correct from the factory is also a mistake. Our old regulator was corroded and the points mostly burnt up, so we bought a new one. Installed it on the car, and it didn't work. The reverse cut-out would turn the generator off if the voltage dropped below 14.4v. Thanks for nothing! https://www.facebook.com/1956Buick/photos/a.568738759868333/568738993201643/?type=3&theater

Edited September 24, 2018 by SpecialEducation (see edit history)

[Beemon]

The regulators from NAPA have screw on covers. That's how I adjusted it like in the book. It was $120 but so far has been bullet proof. I was just curious because when I talked to the man, he assured me that all delco generators used the same field coils and armature from when 12V generators first came out to the advent of the alternator. So what constitutes a bigger generator? 

[Bloo]

More current handling ability in the armature. I doubt they are all the same. It wouldn't surprise me too much if the replacement parts are all the same now. Maybe everything has been superseded to the largest one?

[Beemon]

I know there are obvious case differences the closer you get to 64. I believe it's the Buick and Cadillac generators that use the heavy cases, with the Cadillac having the ducted shroud? Anyways, the info is dead info on the web so I thought I'd ask. Thanks for all the information! 

[old-tank]

Gm cars up thru 1962 had 45 amp generators (looks no different than 30/35 amp generators except for a small diameter pulley) available on A/C cars and used a 45 amp rated voltage regulator (45 amp regulators are available ---  rockauto).  On commercial cars and police cars there were generators available that were larger (larger physical size and output) with matching voltage regulators.  I have not seen or found any of those commercial units other than the one I took off a 55 in 1980.  When I got the car the system was not charging correctly and the voltage regulator has been "messed with"; it worked well with stock 55 parts.  A few years ago I took that generator (much heavier with a 20% larger case) to a shop and they tested it to 90 amps.   I thought about getting a 45 amp regulator, but at twice the cost of a 30/35 amp unit, my frugal nature took over.