There is probably a dead short in the system.
To replace the fuel gauge on a 1992 Ford Bronco, begin by disconnecting the battery to ensure safety. Remove the instrument cluster by taking out the screws and gently pulling it out of the dashboard. Disconnect the wiring harness from the back of the cluster, and then remove the old fuel gauge. Install the new gauge by reversing this process, reconnecting the wiring, and securing the instrument cluster back in place.
The fuel control relay is mounted on the right fender, a foot aft of the battery. It is one of two cube-looking relays mounted there. It is controlled by the Electronic Engine control. Replacement is about $20.
Either your battery is dead, or your alternator has failed.
The battery gauge in a vehicle will move when you use your power mirrors as your causing a small drain on the battery & lowering the voltage slightly. The effect is normally only really visible when the engine is not running.
Possible bad alternator.
Several things can cause the fuel gauge to stop working. 1.The sending unit in the fuel tank may be malfunctioning or broken. 2.There may be a broken, disconnected, or grounded wire going to the fuel pump/sending unit. 3. There may be a disconnected wire at the gauge cluster, or the gauge cluster itself may be malfunctioning.
Having a short in the turn signal wiring can cause gauges to fluctuate. If the battery gauge is fluctuating corrosion on the cables can be a possible cause.
What year is your car? Did you mean the CHECK ENGINE light? The battery gauge?
Its a sign that either your battery or alternator is starting to fail.
it works in side the battery
The temp gauge may stop working on an 89 Ford Bronco if it is defective, the temperature sensor is damaged, or the wiring has come loose. All can readily be fixed by checking each component separately.
There are a variety of reasons from a bad sender or gauge to low oil level to worn bearings. Check the sender first as it's the easiest.