Does Alternator Draw Power?

If your alternator isn't working correctly, it can't power your battery effectively, which can make it hard to start your car even if you were just driving! If your car won't start after driving, there's a chance it might be your alternator.

Can alternator drain battery when car is off?

A corroded or defective alternator diode will faultily continue charging the circuit even when the car off. This, in turn, will drain your car battery and cause the car not to start.

How much power does an alternator draw?

An alternator takes about 1 HP for every 25 Amps of power. At full output, a 100 Amp alternator will need about 4 HP. For a long time, most alternators don't operate at full output.