you can tell if it is the selector down on the passenger side frame rail if you get under the truck with the ignition on, truck off. Have someone switch tank switch, you will hear the selenoid click, if no click, run a jumper wire from the battery to the long post on the switch on frame rail, if when you hit this switch with the jumper you hear the selenoid click then for sure it is the dash switch,<p>or<p>if you have a current light, ground it to the frame and hold it on the pos wire going into the unit when you have someone switch the tank switch, if no power, check for power going into the switch, if power not going into switch follow line to fuse block<p>i assume you already checked the fuse for the tank switch??<p>-abe<br>