It's a 93, correct? If so, following is from the 96 Bronco Owners Guide from HILLER FORD
it's for a 96, but most in it is = to 92-95 exc for Anti-Lock Brake (ABS) - RABS (RABS II 87-92) & 4WABS (93 - 96);
& Air Bags in 94-96 Bronco
Charging System Light
This light, shown as a battery symbol on your cluster, indicates that your battery is not being charged and that you need to have the electrical system checked.
The charging system light This light comes on every time you turn the ignition to the ON or START position (engine
off). The light should go off when the engine starts and the alternator begins to charge.
If the light stays on or comes on when the engine is running, have the electrical system checked as soon as possible.
Are you using a Multi Meter or voltage meter for the reading or the "voltmeter in intr panel?
a normal battery that is fully charged produces 12.6 volts, not just 12.0 V. Remember, when measuring battery voltage, everything in the car should be off, or the battery should be disconnected. Voltage measurements are always "no load" measurements unless the battery is being tested for it's performance under load
Slow Cranking or a Grinding Noise; "... Problems with the negative battery cable is a major cause of starting problems in Ford, Lincoln, and Mercury vehicles. Bad battery cables can cause slow cranking or a grinding noise when trying to start an engine. On some late model vehicles dating back to 1994, the wire connection inside the battery terminal connector corrodes easily. This will cause a voltage drop in the cable and result in low voltage being supplied to the starter. You can check for voltage drop in the cable using a digital voltmeter. Connect the negative probe of the voltmeter to the negative battery post (not the battery terminal connector). Then connect the positive probe to the starter case and crank the engine. The voltage reading should be less than .5 volts. A higher reading means there is resistance in the cable or the battery terminal connector. Clean the cable end and the battery terminal connector and test again. If the voltage reading is still higher than .5 volts, replace the cable and the battery terminal connector..."
Source: by genco1.com