What do you mean by "frying" the battery? If you're referring to it overcharging, the alternator can't cause that directly. That's a problem with the voltage regulator inside the Engine Computer or the wire going to it is shorted to ground.
The place to start is by measuring battery voltage when the engine is idling, but you must do that when the problem is acting up. The voltage must be between 13.75 and 14.75 volts. If it is higher than that, the water will start to boil out of the acid in the battery. Over time that will destroy the battery.
If the battery is becoming discharged, that will not destroy it but eventually it won't start the engine. The most common problem is worn brushes inside the alternator. They can be replaced on some models without even removing the alternator from the engine. The clue to diagnosing the system is to measure the two voltages on the two small wires on the back of the alternator. That must be done while the engine is running.
caradiodoc
Feb 6, 2011 at 2:06 AM
