hi all. I have a truck that was originally a 77 3\4 ton that was equipped on the dash for dual tanks (with the switch)..when i got the truck it only had one tank on it. I've since changed the 77 cab to an 81 and this cab also has the switch for dual tanks. I've determined that the sending unit in the tank is defective by using a ohm meter and temporarily run a jumper to by pass the corroded center pin strap on the lower section of the sending unit and now get reading on my meter..i'll replace the sending unit but have it like this just to try and get my fuel gage to read something other then way past full (3 oclock position)..The wiring under the truck is a rats nest for the fuel sending unit and am trying to trace out what is what. I'm only ever going to have one tank on this truck. The wires in this newer cab seem to go to a relay of some sort located beside the main fuse block then to the switch on the dash. I go under the truck and can't seem to get voltage on any of the wiring for the sending unit (s)..My main questions i guess are 1.) whats this relay between the switch and fuse panel and could it be defective? 2.) what voltage should the sending unit be getting? 12v or a lower voltage that comes from that relay. In the meantime i'll pickup a new sending unit but also trying to have the right voltage\wiring ready.. the original wiring harness\fuse panel from the 77 used glass type fuses and the new cab has push in auto fuses.
advice would be very helpful..
confused as hell, Jeff