The Stovebolt Site Forums The Shop Area The Electrical Bay Gas gauge resistor

I'm sure this has been discussed before but the "search" funtion is not helping me with the answer. I'm converting my truck from 6 to 12 volts and need to place a resistor in the gas gauge circuit; what size should it be? I have a Radio Shack here locally and just need to know the values for the resistor (I know these are sold from commerical websites but want to get it locally). Thank you.

ron

For a 1948 to 53 truck you would need a 30 ohm 2 watt resistor. If you are talking about a different year then it could be different. Check the resistance of the gauge from the power connector to ground and see if it is near 30 ohms.

10/4. I checked it and found 31 Ohms. Radio Shack has 33 ohm resistors, 1/2 watt; should this work?

ron

Question:
Are you guys using the resistor to be able to use the original 6v dash gas gauge ? or is it because of the sending unit in the tank ? or both? I'm putting a 12 volt gauge cluster in...do I need a resistor inline for gas gauge ?
Thanks

The power dissipated in the resistor would be VxV/R or 36/30 which is a little over 1 watt. Therefore you should have a resistor with a rating over 1 watt. I would suggest 2 watts.

I am converting my 1946 Chevy Suburban School Bus to 12 volt using the voltage reducer Jim Carter sells.

It is specifically sized for your fuel gauge @ 1 amp.

The Jim Carter part number is EL311 which is a one amp "Runtz" voltage reducer.

I have one of these but have not put it in yet since I am still doing body work. I have just started refacing my gauge assembly.

While we are on the subject, where should I place this reducer?

I am guessing that it should be on the power input side of the gas gauge to step the voltage down to 6 volts from 12. Am I correct?

Yes, and the direction of resistor might be important. The ones that I have used had an "open" end (round-hole end or slotted end) on the gauge side of the resistor and a screw/nut for the hot-side connection on the resistor.

dave, I have a Runtz from JC that I did not use. It had a letter of instructions in it. Do you want me to copy and send them to you?? If so drop me a PM.

Uncleb, we're practically neighbors. I'm in Santa Rosa.

When I first got my '36 Chevy pickup in 1965 it was all original and I foolishly made a rat rod out of it. Part of that was converting it to 12 volts. The dad of one of my friends worked at Lockheed and fully understood instruments like my gas gauge.

The short version on the gas gauge was that he told me it would work on 12 volts without any resistor. I know he was right because I ran it on 12 volts as a daily driver rat rod for about 50,000 miles before restoring it back to original in the early 70's. If you want to know WHY the voltage made no diference I'd be glad to give you the explanation he gave me.

A lot of unnecessary adaptors are sold. Here's another example. I moved to a rural area with no natural gas hookups in 2001. Adaptors are sold to "convert" stoves from natural gas to propane fuel. In reality, all the "conversion" required was adjusting the metering screw on each burner tube to get a neutral blue flame!