How do you tell the difference between bosch or valeo alternators on a 2000 NB 2.0? The alternator tested bad so it appears that it should be replaced. Are there any other causes/problems that would result in the improper charging of the battery? I will probably have it tested again before replacing because during the previous test the car had a bad MAF sensor and wasn't running correctly with it plugged in. With the new sensor the CE light cleared and the car seems to be running properly.