Gas Guage sender the sending unit is just a variable resistance in the negative side of the gauge--instead of the gauge being grounded directly from the "s" terminal it goes through the sending unit, back to the ground wire attached to one of the sending unit mounting bolts, and then to a good chassis ground. So it won't work if a. there is no 12 volt + to the 'I' terminal on the gauge, b. the wire to the center of the sending unit isn't attached at it's other end to the 's' terminal of the gauge, c. the sending unit doesn't have a ground wire attached to one of the mounting bolts, d. the gauge is bad, or e. the sending unit has much too high an internal resistance. It sounds like you don't have 12 volts + to the gauge. If you don't, I would supply that directly from any hot source directly to the 'i' terminal, even directly from the battery to see if that is the problem--but install a very small amerage in-line fuse in your temporary power lead--like .5 amp--since a gauge uses practically no amperage but if there is a short that fuse will blow immediately and protect the circuit. If it still doesn't work then w/o much work the back seat comes out, the rear panel comes out, the vent tubes crisscrossing above the tank come out, and the sending unit lifts out--without pulling the tank or a bunch of hoses--just the one connecting in the top center to a 'T' in the vent tubes. Then you can manually lift and lower the float arm and see the gauge move. w/ power to gauge 'i' terminal, center wire of sender still wired to 's' terminal, and a ground wire attached to one of the holes in the sending unit mounting plate. You can put an ohm meter on the center terminal of the sending unit, the other lead on the mounting plate, and with your 3rd hand move the float arm to max and min postions and note the resitance range, as well as at intermediate positions. Also I believe the resistance on the gauge itself between s and i terminals should be about 90 ohms. But if you don't have 12v + power to the i terminal that's probably what's wrong. Good Luck. Keep us all posted. Dave '78 RQB2670 June 2001 If you take the sending unit out of the tank and soak it in a solution of Drano (1 tablespoon in a bowl of water) for 1 hour, that should free up any crud and corrosion inside the unit. Rinse well afterwards and don't soak the float itself. It should be fairly easy to take the sending unit out of the tank - access hole is in trunk. Be careful and don't drop any crud into the gas tank. "Dan Streb" Jun 2003 ----------- You cannot "ground" at the gauge as this is not how fuel gauges are wired! The ground wire at the sending unit acts as the "input" to the sending unit (really just a variable resister) with the lead from the center terminal (stud) being the output to the gauge. Current flows FROM negative TO positive (NOT , as most people believe, from positive to negative)negative "gives up" electrons, positive "grabs" electrons. By wiring a fuel gauge in this manner you reduce or eliminate the possibility of sparking across the wiring in a sending unit! (A GOOD thing...NO?) Also, check www.stewartwarner.com for a distributor in your area as they will carry the newer "thick film" style sending units (a FAR more reliable, solid state, version) for around $21.00!! For my 82' a #385C-F was an EXACT replacement and will last about 3-4 times as long as the orig. resistance / wire wound style did! You do have to crimp on a ring style terminal in place of the stud mount terminal (that was stock on my 82')and set the depth on the new sending unit (I seem to remember 10-1/2" being correct) but it is WELL WORTH the effort as the gauge functions far more smoothly. One last note, it DID make a difference which sending unit mounting screw I attached the groung wire to as to how well the gauge functioned. Beware of vendors trying to get rid of their old stock of wire wound sending units and if your oil pressure sending unit is bad GET THE THICK FILM VERSION!!! It will out live the stocker by a factor of 10!! Also around $20.00 at my distributor in Batavia, IL. Oil pressure sending unit #279A. Tom Gorr RQB3449i July 2003 ----------------------------------------------------------- Sender for Hawk NAPA Balkamp # is 701-1574A measure accurately before cutting...