View Full Version : Alternator voltage?

Todd Brosius
09-18-2007, 08:40 PM
If I were to place a volt meter on my '04 MCX alternator what volts should it read with the motor running? I have Perfect Pass and when I check what it reads it tells me 13.7 to 13.9 volts when the engine is running. Just making sure my alternator is charging my battery properly. I'm guessing it was the fault of my battery not holding a charge correctly and my battery dealer honored my warranty by pro-rating it out. He thought the alternator should charge a little over 14 volts when running.
Thanks for the help in advance.

09-18-2007, 09:15 PM
your charging system sounds fine. you would need to load the system to check the max amperage output but most people don't have access to a charging system load tester.

put a battery tender on it if you store it for any length of time. I take my battery out in the winter and leave it on a tender. I'm still lucky to get 3 yrs on a boat battery.


09-18-2007, 09:37 PM
Unless the alternator has an adjustable external regulator, there's not much chance that it will put out 14+VDC at idle. At 2000+RPM, maybe but definitely not at idle. Yours sound fine.

09-18-2007, 09:39 PM
If the battery goes dead in about three days, put an ammeter on it. If the draw is about 300mA, remove the charging lead from the alternator and if it goes away, the bridge is bad. It'll still charge but if the rectifier is bad, AC is going along for the ride in all of the circuits, which isn't how they were designed to operate. If it's not AC, it's ugly DC voltage.