Electrical help needed!

[computerworks]

Buzz...
do you have a wiring diagram?
Listening to the fuel gauge "not responding" unless the lights are on...seems to indicate a miswire or an "open" with a 'sneak-path' back to the fuel gauge (maybe a grounding problem at the dash)

I would check the diagram and see if the fuel gauge fits in with the light circuit.... shouldn't.

Fuses are thermal-responding devices, so a high amperage fuse will be warm to the touch when its circuit is carrying current.

Was the fuse the proper rating? If you have the diagram, look and see all the lamps that are powered by this circuit, find the specs on the bulbs and add up their operating current (in Amps).
The total current drawn by the circuits should typically be 75% of the fuse rating... if they all add up to 15 amps, use a 20 Amp fuse.

Is your fuse box in a very hot area? If so, you may have to up the fuse value slightly to "derate", or compensate for the extra heat.

Last observation.. is this lamp circuit also powering the instrument panel lights? .. if so, you may have a wire misplaced on the fuel gauge, such that indicator lamp voltage is powering the meter not the lamp.

Hope some of this helps.