Thread: Voltage reads 13.1-13.5 while running

Originally Posted by lewis1952

Your voltage should be 11.5-12 volts when resting and no more than 13.5 when running. The alternator shouldn't put out more than 14 volts, remember this is a 12 volt system. I have a 1999 Freightliner I use around the farm. It has 3 batteries and the alternator only puts out 14.5 volts.

Pretty wrong, the alternator should put at least 13.5 to 14.5 volts always.

You'll see upwards of 15 volts on really cold starts and while idling to get the engine warm, then drops to normal.

Every single car that I do charging system checks on reads atleast 14 volts at some point in time.