What would cause the charge light to come on followed by the gas and temp gauge to drop off on a 1987 Toyota pickup battery appearers to recover its charge after it sits for awhile?

Answer 1

The battery it self does not recover charge; The internal resistance of any battery will increase as it heats up - A good example is how a flash light with near-dead batterys will light the bulb for a short time, and then dim-out. If you turn it off and wait, it will repeat the process (The process of dumping available current into the lamp and then leveling-off to a zero discharge state.) The issue becomes that the potential energy (Stored in the battery) cannot overcome the resistance (of the lamp filament) - Therefore, no more current can pass through the lamp.)> With your vehicle, the same case is true - the battery, when not in use, will seek an equalibrium with it self. Once the battery cools down, the internal resistance will decrease, allowing it to apply more current to a load. Since the battery is actually below a reasonable voltage (Below 12 Volts) - there isn't much "pushing" the current that's available in the battery before it levels back to a zero discharge state. (Zero discharge state = resistance the battery needs to overcome is greater than the potential that battery has to overcome the load.) If your gas and temperature guages are electronic, and the ignition isn't on (Car not running and battery dead) - The guages will not function because they are reliant on the electronic sub-systems that provide measurements to those guages. (They are in effect "un plugged") The difference between analog and digital guages - analog guages provide proportional measurements and digital guages provide calculated measurements.