WC Fuel Gauge Adjustment

[shrinx]

I recently had the gas tank of my WC-27 (’41 Ambulance) reconditioned. While I was at it, I purchased a new sending unit. The one on the tank had apparently disintegrated decades earlier.

A previous owner had converted the electrical system to 12V and replaced the fuel gauge with one rated for 12V. But now when I connect them, the indicator on the gauge reads from “full” to “very full.” So I have is a sending unit and a gauge that are incompatible without some tweaking.

From information I gathered on the Internet machine, it appears that I need to add some resistors somewhere in the circuit, but when it comes to electrical issues, I am a complete moron.

I need help determining what resistors to put in the circuit and where to put them. Any advice will be welcome so I can go from “Well I think I have enough gas to make it, and if not I’ve got a can of gas in the back” to “Look! The gas gauge shows half.”

Here are the specifics:
Fuel gauge resistance range is listed as 240 to 33.5 Ohms
Sending unit resistance range is measured at 130 (Empty) to 0 (Full) Ohms

Thanks,
Terry

[Doc Dave]

Terry,
If a search of this forum is not helpful, there is a ream of information on the plymouth-dodge car and truck forum.
Look at this among other ones:
http://www430.pair.com/p15d24/mopar_...+gauge+trouble

[mannyc]

you need to match the gauge and the sender

first remove the sender from the tank and hook it up to a multimeter. measure the high and low resistance levels and ascertain what type you have. try to determine if your fuel gauge is 6 volts or 12 volts. most ww2 dodge fuel gauges are 6v and required a resistor on the power side to drop the voltage. the senders were 6volts. if you hook the gauge and sender together in a test bench setting, you will get a better handle on what you need. i purchased a device called a runtz that drops the voltage in a solid state format instead of the heat dissipating type that was used in the orig units. any questions, email me directly.

[shrinx]

Running on empty no longer

Thanks to Doc Dave and mannyc for the help in solving my problem. I now own something called a multimeter and with some fiddling with various resistors have been able to get the gauge to register 1/2 to FULL. I think success is within just a few more trips to Radio Shack.

Terry