Working on a hot rod 72 Jeep with the all in one speedometer fuel and temp gauge. It has a new sending unit but the old tank from the po wasn’t hooked up. So this never worked as far as I know since the temp tank. We have 12 v to top right terminal as you look from behind, sending unit wire on top left, flat gnd from temp gauge to fuel, ran volts down the sending unit wire and had 9v at end of wire. Also we tried a separate gnd to the gnd on both sending unit and gauge separately of course and putting 12v to the s/u terminal the gauge goes to full. We’re at a loss at this point.