The Stovebolt Site Forums The Shop Area The Electrical Bay 56/3200 12 or 6 Volt?

Hi Guys,
Just wondering if anyone knows what voltage a 56-3200 was originally. I know that F@@d trucks didn't change to 12 Volt until 57, but not sure about Chevy trucks.
Thanx,
Gene & Jr

I'm pretty sure it was '55 for Chevy.

12V from early 55 - took longer for Ford to figger it out

Bill

Ford started 12volts in 56.

Hey Gene,
My '56 6500 is an original 12volt so I'd bet yours is too.

Chevrolet trucks changed to 12v (negative ground) in all second series 1955 trucks (from 6v negative ground).

GMC trucks changed from 6v positive ground to 12v negative ground in 1956.

There were 12V gmc trucks prior to 55. My '39 to '53 gmc parts manual lists a dropping resistor for the fuel gauge, 12V starter, and 12V generator.

V8 GMCs were 12v in '55.2. Only the I6 models retained the positive ground 6v system.

reo_guy, those were all heavy-duty trucks.

GMCpanel, the applications listed start with the 100 series. So it does seem that one could have had 12V 1/2 ton prior to '55.

Maybe the '39-'53 GMC parts manual has that resistor because so many people had converted to 12v by the time it was printed? Check out page 24 in this 1955-2nd GMC truck brochure. It seems to confirm GMCpanels information.

Tim

Some of the military GMC were 24V. The dropping resistor reo_guy saw listed may be 24V to 12V. I'm almost certain there were no 12V civilian trucks, 2-ton and below, before the V8s as GMC panel has listed. I think some of the larger GMCs may have been 12V before but I don't have documentation on what models.

The parts manual was printed in 1953. It is the light duty master parts book for models 100 through 370. There is an asterisk next to the 12V part numbers (and other options such as hydramatic). The legend for the asterisk states "Determine if option required." The starters and generator descriptions specifically state 12V. It is obvious that 12V was in fact available. Maybe not standard, but still available.

The M211 and M135 military trucks were 24V. Their predecessor, the CCKW was 6V. I had a pair of the M135 and my brother has two CCKWs.

reo_guy, it's in my '54 book too, listed for models 100 on up. It lists 12V headlight bulbs like they used before sealed beams so it seems this might have been an option as early as '41.

Hmm...that's a weird one. Someone needs to bring this up as a discussion over on the Old GMC board - the last I heard, no one over there had ever heard of a pre-55 12v light or medium-duty GMC. Some of them have been in this old truck biz for a long time - but if it was an option, I'd love to hear the details.

What is unusual is that there is no mention in the light duty service manual. If anything, it must have been a rare option.

what you hafta keep in mind is a parts book covers up to the year it was published, and will include some things that became standard practice after the manufacture of the earlier vehicles - as soon as GMC had used 12v for any application, shops would have been "updating" previous models - GM would simply have made adjustments to parts listing to make it easier for parts dept's to sell folks what they were asking for, and be sure it would fit the application

Bill

Is there a possibility that GMC offered parts and/or accessories for dealers to use when a fleet/commercial/government customer submitted a bid with specifications that required a 12v system?

I ask this because the 1955 GMC Sales brochure makes specific reference to providing new RPOs to meet 12v bid-specifications, especially for school buses and larger trucks. Having RPOs instead of parts/accessories would make life easier for a GMC dealer. Just a guess.