How To: Diagnose Charging and Battery Issues

FC Zach · \r\n \r\n \r\n 03-17-2008, 09:21 PM\r\n \r\n \r\n

The proper way to do it is via the FSM. However, the below method is quick and dirty.

The DMM (Digital Multimeter Method)
1. Turn on the engine, headlights, heater, and fan on high.
2. Test the alternator output by measuring the voltage between the alternator positive post and the alternator frame (13.5 to 14.4 volts).
3. Test the primary battery positive (+) wire by measuring voltage between the positive battery terminal and positive alternator post (0 volts).
4. Test the primary battery ground (-) wire by measuring voltage between the alternator frame and negative battery terminal (0 volts).
5. Turn off the engine, but leave the lights on.
6. Test the battery by measuring the voltage between the two battery terminals (~12.5 volts).