How to I test Alternator output to my batteries

[JField]

My 2007 Ram 3500 Laramie 5.9 doesn’t appear to be charging the batteries. The guage used to charge around 14 volts but doesn’t appear to be charging now.
How can I measure the level of charge coming from the Alternator to the batteries using a multimeter.

Thanks for any help.

 

[BigPapa]

Measure voltage without the truck running and then again with the truck running. I'd check them with it running after a short drive to make sure the grid heater is off and the alternator has had a chance to kick in.

 

[Topzide]

Just simply put meter on the terminals, if charging, voltage will be above 13.0 volts. Resting battery voltage is 12.5 - 12.8 volts on average. Set multi meter to DC volts when testing.

 

[Ozymandias]

The factory gauge is a lie-o-meter, it shows what ever the ECM wants to show you.
Take a multimeter to confirm. Also measure the battery's independent resting voltage.
If that all is good you can use an amp-clamp to measure current with the engine running.