View Full Version : Charging system checkpoints

08-19-2010, 03:44 PM
I changed out worn brushes in my alternator with good ones, but things are still up in the air. Using a multimeter at the battery post's, its around 13-14.2v, and measuring at the alternator bolt, and ground, its around 13-14.2v also. But I have a cigarette socket tool that shows voltage, and its showing 9v-13v (varies, but mostly under 11v). **Just tried using the socket tool with just electric/battery power, key turned ON, and it varies between 9 and 11v at socket** I've tried the tool in a newer car, and it shows above 14v, so it is accurate.

My question is what is going on? Why under the hood is it showing relatively normal voltages, yet the cigarette socket is underpowered. Is there any other checkpoints in the car I can check the 12v line? I don't want anything getting damaged from low voltage.

Ok, so I went out to drive again, now its showing steady 13.5v while idle/driving, and ~13.8v at the battery post. Is this good enough to charge the battery? And the 12v socket is still jumpy 10-12v on electric/ON power...weird...

**EDITEDIT** - Cigarette socket tools a piece of crap, sometimes its off and jumpy, re-plug and its good.

08-19-2010, 11:50 PM
You should get around 13.7-14v at idle at the battery. So it sounds like you're within the normal range, and yes, it's good enough to charge the battery. Check the voltage with some of the accessories in your car turned on, i.e. headlights, heat, radio, etc., and see if this makes the voltage drop. Your alternator should be able to handle the factory accessories turned on without too much voltage drop.