Hot Rods How to tell if 12v conversion already done?

Hi all,

I just bought a '49 Chevy truck and I'm trying to tell if a 12v conversion has already been done. My assumption is yes since it has what looks to be a newer alternator attached to the engine, but im not sure. it has a box that is faded but I can read C. E. Niehoff & Co that looks like it could be a converter but I don't know. There's not a battery currently in the truck, but the owner added a battery tray right by the motor and dated that a new battery was put in March of 1985.

If I hook up a 12v battery will it cause any problems if I try to start it or are there any other ways to tell? I don't have a voltage meter to test it.

 

Check the voltage of the headlights and other bulbs

 

Didn't have headlights or an interior light bulb unfortunately. It was sitting next to a barn for at least 5-7 years.

 

If it has an alternator, it is almost for sure 12 volt.

 

If it has a working alternator installed, it's 99.9% sure it's 12V. I've only ever seen one 6V alternator and it was a huge thing, with a separate rectifier the size of a small toaster oven (and put out nearly the same amount of heat). It was in a '46 Chevy coupe that used to belong to the Seattle fire department. Other than the lights, about the only 6V bits that may be harmed by overvoltage for a brief period would be any electric gauges and a OEM radio. Any motors will run fast but would be fine for short periods.

 

Niehoff makes brushless alternators from 14 to 78 volts so it must have been converted.

 

No bulbs to burn out then put a 12 volt battery in it. The coil may or may not be marked with 12v. Is there a ballast resistor? Take the battery out of your daily driver and try it rather than buyin one. You got nothing to lose that way.

 

If it has the original gauges, take a look at the ignition feed wire and see if there has been a volt-a-drop or similar resistor installed. If not; just disconnect the gauges for now and go with
12 volts.

 

except for all the Model A guys who want to stay 6 volt I have a 6V alternator for my Model A. Its pretty common

 

I had a 6 volt alternator on my 54 Chevy. Worked great. Regular sized.

If the battery cable is a standard cable it's almost certainly been converted. 6 volt needs a larger cable to work for very long and reliably. OO cable for 6 volt.

Maybe all the bulbs are gone because someone tried the truck on 12 volt? (will start fine, but will blow the bulbs).

 

If you examine the alternator closely it may have the voltage and amp rating stamped into the case.

 

can take the alternator off and get it tested , if it puts out over 12 v its a 12 v , if its over 6 v but under 8 its a 6v .

 

just wire a light into the system six or twelve it will let u know.

 

LOL, if it doesn't have a battery in it now, wouldn't that sorta depend on the battery you install? There is no difference in the wiring between 6v and 12v other than the size of the wire (6v is heavier gauge). If it is the original wiring it will work with ether one, if it has been rewired, the wire size would tell you. But only if it was done properly, so most likely no help.
The only things that are going to be different between 6v and 12v is the alternator, maybe the starter (but then again maybe not), maybe the coil (but then again maybe not depending on how the resistance is wired to it), also on the coil if it was changed from positive ground to negative ground the coil wiring should have been switched. The only other changes would be voltage reducer resistors to items like the gauges, wipers, heater, etc.
Why not just decide what you want it to be and set it up that way, fairly simple. Only real issue is the alternator.