I have a 38 pickup and it has been converted over to a 12 volt system because it has a fan for the radiator. I have a separate gauge cluster for temp, oil pressure and voltage. But I still have some original gauges and I'm not having any luck getting the fuel gauge to work. Has anyone had success with using the original type 6 volt gauges with a voltage reducer in a 12 volt system?

Camile
I cannot see any issues with your idea though I have never tried it. While the voltage remains under 7 and definitely under 7.5 all of the original equipment will be happy.
Tony

Google search Runtz resistor. One is needed for the gas gauge and each 6 volt accessory.

For the gas gauge, a 30 ohm 2 watt resistor should work just fine. The gauge is easy to test.

Any suggestions for a good step down from 12 volt to a 6 volt heater motor in my 1955 1st Series pickup? I tried a regular one and it heated up badly. Or should I just swap out the 6 volt heater motor for a 12 volt?

If the gas guage was not addressed when it was converted to 12 volt, it is probably burned out.

The fuel gauge works on varible resistance. You will never get an accurate reading with a resistor voltage drop. You could also burn out the gauge and sending unit and possibly explode the tank.
If you spend 63 cents for a 7806 voltage regulator from digikey.com, you will have a constant 6 volts negative ground to the gauge.
For details, please check out my webpage: <http://home.znet.com/r1937/Fuel.htm>.
Good luck, Lou

FWIW and to add a bit of mud to the water I'll tell you about my experience with this very issue. As a strapping lad in my early 20s I bought a 55.1 Chevy panel truck. It was 6v. I converted it to 12v. In doing so I replaced the battery/coil and light bulbs. In my ignorance I put no resistors on anything. I put over 100K miles on the truck with no electrical issues whatever following the conversion. Having said that I'm not recommending you do the same thing. I may have just been lucky. My point is that the assertion that you'll fry everything unless you put resistors on them may not hold true in all cases.

A while ago I did a little research on my bench with a 38 Master gas gauge sender and gauge. I found that I could vary the voltage quite a bit without affecting the reading much. I used my variable voltage supply to do this. Many folks use a resistor for the gauge feed with great success.

A 6 v. system converterted to 12 will burn your gas gauge out.. My 54 suffered that twice,, standing on your head to replace that gauge is a bear.. Use a resistor...Ps probably your radio too..All bulbs..headliner bulb.. dash lites..Patricks..Casa Grande Az. has a great reference sheet