Farmall Super C Lights

Bookman

Member
I have a Farmall Super C that has been converted to 12 volts with an alternator. Can I just replace the light bulbs with 12 volt bulbs or do I have to replace the light switch too?
 
For the most part a switch doesn't care if it is 6 or 12 volts. So yes all you need to do is replace the bulbs or wire the bulbs you have in series so both both have to work for or you have no lights
 
Thanks. I was wondering since I saw both 6 and 12 volt switches being sold. I got some 12 volt bulbs.
 
The big thing is with a switch is amp draw. So if you have a switch rated for 10 amps you cannot use it in a 30 amp circuit. Volts are not the problem it is amps
 
I take it from your first response that I still do not need a different switch though....right?
Thanks
 
No you do not need a new switch matter of fact going to 12 volts cuts the amp draw by almost half by the lights so the switch is likely to handle things better on 12 volts then it did on 6 volts. On almost every thing if you double volts you cut amp draw in half
 
For the same wattage bulb, a 12v bulb will only take 1/2 the amperage of a 6 volt bulb. Example: a 36 wattage 6 volt bulb will take 6 amps. 36 watts divided by 6 volts = 6 amps. For 12 volt
36 divided by 12 volts = 3 amps. So a 6 volt switch should be able to handle twice the wattage when 12 volts. Therefore your 6 volt switch should be plenty good with lots to spare
 
Bookman, the letter series Farmall light switches had a "Dim" and "Bright" setting. On Dim, it ran the headlight circuit through a resistor on the back of the switch, probably about a third of the resistance of the bulb filaments. With 12V bulbs, the filament resistance will be double, and the resistor (at roughly a sixth of filament resistance), isn't going to have much if any noticeable effect. For all practical purposes, your lights will work just fine with a 6v switch. If you're aiming for "like original" operation, you'd need the 12v switch.
 

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