Wiring a Fuel Gauge for a Chevy 1973 Truck

It is imperative to know that not all fuel gauges and sending units are alike. Chevy, Chrysler and many foreign vehicles use different resistances on the products. A 1973 Chevy truck fuel gauge uses a 0 to 90-ohm gauge and corresponding fuel sending unit. Keeping in mind that a fuel gauge operates on the amount of resistance to ground that the fuel sending unit introduces, any additional resistance in the circuit will give an inaccurate reading or none at all.

You will need the following tools to complete this job:

Matching gauge and sending unit with a 0-90 ohm range for a Chevy truck
Box of assorted wire terminal ends
Wire crimping tool
Wire cutters
¼-inch drive ratchet
Set of ¼-inch drive sockets
Voltmeter
Roll of 14-gauge wire

Supply power to the positive terminal on the back of the gauge. The power supply must be fused and switchable, meaning the power should only be present with the ignition switch on in the run position. The best locations are the accessories side of the ignition switch or at the accessory fuse under the dash. If the gauge is just being replaced, a wire should be present from the old gauge.

Check for the power wire using the voltmeter. Turn the key on and check the existing wires for power. Turn the key off and make sure there is no power. Attach the 14-gauge wire to the source of the power, using a blue 14-gauge butt connector and crimp it with the crimping tool.

Connect the G, or ground terminal on the back of the gauge to a good ground, preferably the frame, using the 14-gauge wire and a circular blue terminal. This terminal allows the terminal to be installed over the stud terminal on the back of the gauge. Do the same for the opposite end. Make sure that the surface used for a ground is free of rust and paint so that it makes a good contact.

Connect the sending unit wire from the S terminal on the back of the gauge to the sending unit in the fuel tank. Attach a circular terminal end on both ends and attach one end to the S terminal on the gauge. Pass the wire through the firewall, along the driver's side frame rail, attaching it with wire stays along the way to the fuel tank. Access the top of the tank by lifting the bed. Lifting the bed just requires removing the three frame bolts on either side of the bed, using a 3/8-inch drive ratchet and socket. Lift the bed enough to gain access to the top of the tank. Prop it up with a piece of board or something suitable. Connect the sender wire to the center post on the top of the sender.

Connect a ground wire from the G blade terminal on top of the fuel sending unit to a good ground on the frame. The ground must go to the frame, not the body. Attach a blue female blade end to a 14-gauge wire, then crimp it down. Place it on the blade terminal on the sending unit. Connect a blue circular terminal end on the opposite end of the wire. Bolt it to a good clean spot on the frame. Lower and bolt the bed back into place.