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Disassembled gauge with soldered LED resistor mod and labeled il…

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The light can be placed anywhere you like. I chose the lower L end of the fuel level scale on the gauge face since it's intuitive. I drilled a hole the exact size of the lamp for a press-fit. It may also be placed directly behind the fuel pump icon, but it won't be as distinct, especially in daylight.
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Any 12V lamp can be used. I chose a red LED for its long life & low current-draw, which also requires an inline current-limiting resistor ( http://led.linear1.org/1led.wiz ). An incandescent 12V bulb doesn't require any resistor, but it needs more current, which means it gets hotter and the heat might affect the gauge face. Since this lamp is bare on the back, and since it's placed very close to the cluster illumination, I spray-painted its back so light wouldn't leak in, making it look like it's on when it's not.

One side of the lamp must be connected to a 12V feed. I chose the IGN terminal of the fuel gauge because it's convenient.

The other side of the lamp must be connected to the ground output terminal of the module. I chose to use a yellow wire since the fuel level circuit is Y/Wh. The module slot is a convenient route for the wire which doesn't require any drilling of the cluster case.

For added functionality, the new light's ground can also be connected to the Inertia Fuel Shutoff (IFS) Switch warning feed. On '92-93 trucks, this is the Gy/Or wire from the GRAY connector pin 5; on later trucks, a new wire would have to be run. Doing so will cause the lamp to illuminate for low fuel, AND when the key is on but the FP relay is off, AND for a tripped inertia switch. The tach cluster is built to hold a bulb for this function, but the tach face has no indicator position, so the bulb isn't installed and the film circuit isn't cut for it. Non-tach clusters have no provision for a Fuel Reset bulb, although the '92-93 gray connector is wired that way.

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