M38 Fuel Sender

[Jack]

My memory might be failing me, but I thought I read a while back that you could use an M38 fuel sender with a twelve volt system as long as the fuel gauge was also 12 volts. True? Not true?
Jack

[wesk]

Yes you can use them together but don't expect anything that resembles an accurate reading. Carry a wood stick under your seat so you can check fuel level.

There are three components to all electrical circuits. They are interdependant on each other. A change to one will change the other two. These components are Pressure (Volts), Current (Amps) and Resistance (Ohms).

An electrical fuel gage system uses a variable resistor (sender) which reacts differently depending on the float position. The calibration or value of this resistor was set based on it's use with 24 volts applied to it. If you only apply 12 volts to it through the gage the result will be a much higher through voltage at the gage. Even if you install a 12 volt gage the much lower output from the 24 volt sender's resistance will result in an even higher reading on the 12 volt gage than it would have read with the correct value resistor for a 12 volt sender.

The above issues apply to all three of the 24 sender type gages on the M38.

It is so simple to just buy a complete 12 volt universal fuel gage kit that will come with all the matched parts. You drill the sender's lid to match the bolt pattern on the M38's tank. You adjust the fl;oat for the height of the M38 tank and it will all work just like it is suppose to.

[Jack]

That's sure simple enough. Thanks Wes.
Jack