Trying to understand my charging system
2013 Thor Daybreak F53 Ford Chassis: My battery light comes on about 30 seconds after I start the engine and stays on. The battery checks good and I am getting 12.7 volts not running and 13.5 volts ru...
Forum Discussion
- Start the engine. Let it warm up for 10 minutes
- What voltage do you read?
- Start vehicle air conditioner on high. Voltage now?
- Turn on headlights high beam. Voltage now?
- No not shunt anything off until the end of the test
- This is a progressive loading test.
Things are not as easy as they used to be. With today's systems the ECU reads system voltage at three points and analyzes the FIELD REPORT of the alternator. If voltage climbs TOO SLOWLY, the check engine light will come on.The ECU compares rotor excitation amperage to how fast the voltage is climbing. A cute test is to connect a battery charger and maintain correct voltage with a heavy load. A ECU can discriminate sample voltages and throw an error code.
Normally when a new alternator malfunctions the light comes on and stays on after the key is released.
The delay makes me suspicious. I would want more proof before condemning the alternator.
Of course there other further tests to be made but this one will do for a start.
