The Stovebolt Site Forums The Shop Area The Electrical Bay gmc fuel gauge in 12 volt conversion

I am switching my 55 1st series GMC to 12 V negative ground electrical system using a voltage reducer for the gas gauge. I have a question about how to wire the fuel gauge properly . I have been told if you do it wrong you will burn out the gauge . My understanding is that it was a positive ground on the original system and on these applications you have to reverse the wires to get to gauge to read correctly. I have included two photographs of the gauge one of the front one of the back on the back there is one post that has some cardboard bolted to it to identify the post function, part of the cardboard is broken off so I can’t tell what the cardboard said. I myself, wrote a positive and a negative sign by the post but I’m not sure that that it is correct. I need someone in the group who is good converting GMC wiring on this gauge. Any help would be appreciated. The part about a gmc positive ground system and how that affect the conversion is confusing me. Note: attached two photos of the gauge.

Whoa there cowboy! The gas gauge has a voltage input terminal and a sender input terminal. If you read the TIP SECTION under "12V conversion" you will see a GMC tip at top, then the 12V conversion next. Read them both and you will have all the info you need.

Neither of the gauge terminals are grounded. The sender is grounded by it's mounting screws to tank (and a backup wire) and the gauge is grounded by the case touching the panel. As far as which gauge terminal is hot and which is sender, other AD GMC owners will have to tell you. You may burn it out by wrong wiring I believe. I see a red wire which is usually hot and brown wire is usually sender. But needs confirmed. Because this says differently. If this is your tag....and if the tag is on the correct terminal. Let a GMC guy tell you what the "E" side terminal is and what the "F" side terminal is. Don't go by passenger side and driver side...... or left and right when conversing.

Bartamos, Thanks for the help and directing me to the Tips section. Have not heard from any GMC guy about what the "E" side terminal and what the "F" side terminal is, power source or sender wire. The tip section here is great.

Looks like "E" side is hot side. That would be the same as your pic I believe. Can't you follow the wires that are on the gauge in the picture? Don't use color red for any wire that is not hot. EVER.
The wires are not attached to gauge any different for pos ground than for neg ground.