Do you mean rheostat for brightness control of dash lights? Usually in the dimmer control switch Voltage regulator for engine operation--inside the alternator
The Main Voltage regulator it built into the Alternator There is also one on the instrument panel to stabilise the voltage to the gauges
You can find the 1984 Ford voltage regulator on the inside front quarter panel. The voltage regulator will be on the drivers side quarter panel.
Sometimes the voltage regulator sticks causing the contact to send current to radio wipers and other switches on instrument panel.
Its down behind the panel above your left foot rest
Four rivets hold the regulator asm on the door panel but the switch is more than likely the problem.
Fluctuation of Automotive Instrument IndicationsI'm not familiar with, nor have any experience with your vehicle, but...Almost all late model vehicles have special, dedicated, voltage regulators on the instrument panel circuit board for the specific purpose of maintaining a constant operating voltage for the instruments.If the output of the instrument panel voltage regulator is fluctuating, then that could cause some, or all, of the instrument readings to "wander."Another possible cause could be loose connections in the circuits for the fuel gauge and tachometer.
Either your IVR(instrument volage regulator) or a faulty connection from the harness to the cluster.
If the Gauges on your instrument panel have stopped working you may have had a voltage converter stop working. This device mounted to the rear of your instrument panel converts the voltage from your alternator to the voltage that your gauges run off of. You can check the fuses with a multimeter and see if both sides have voltage showing, if so then see about replacing the voltage converter.
intrument panel voltage regulator. no doubt had the same problem
On a 1996 Ford Thunderbird : Under the instrument panel , to the left of the steering column ( I'm not sure if it has a cover on it ) Also , the Power Distribution Box ( which is " live " ) is located in the engine compartment , on the drivers side
located next to the starter selinoid on the inside front panel between the headlight and the radiator
passenger side kick panel