Low Fuel Warning Light Switch

Remove fuel sending unit from gas tank. Using a jumper wire, connect negative battery terminal to fuel gauge sending unit terminal No. 3. See Fig 1. Using another jumper wire, connect a 12-volt, 3.4-watt test light between positive battery terminal and fuel sending unit terminal No. 1.
With sending unit float/sensor dry, test light should come on within about 40 seconds. With sending unit float/sensor submerged in gasoline or water, test light should turn off. If test light does not function as specified, replace fuel gauge sending unit.

Fig 1: Testing Low Fuel Level Warning Switch (Typical)