Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Charging system

Here’s the question. Why won’t my battery receive any charge from the alternator? Both are brand new. I even had the voltage regulator replaced. The car starts fine, but the battery won’t read any higher than 12V.

Is the alternator getting a ‘turn on’ charge? Depending on the model of the alternator, there is a wire connector that supplies switched power to the regulator and field coils of the alternator. Without that power, the alternator will not produce a charge.

Also, the line between battery and charge terminal of the alternator needs to be checked to see if it is burned out. It is a fusible link wire designed to internally melt if a power spike goes through it.

Bad voltmeter?

The voltmeter is fine. I checked the battery with a multimeter while the car was running.

Well, I’m sorry to say this, but I have no idea what a ‘turn on’ charge is. The car is a 1982 Corolla, so it’s not very high tech. I checked the wire, though, and it’s not burned out or anything. All I really know is that everything is fine and works individually but not as a whole.

I tried to explain. There is an electrical connector on the backside of the alternator. You need a wiring diagram to know what the voltage at these terminals are supposed to be. But, if there is no power at this connector, the alternator will produce no voltage to charge the battery. For this '82 Corolla, idk if it is a 3-wire or a 5-wire connector.

Try running the engine @ 2,000 RPM’s for thirty seconds. Some charging systems require that the alternator be spun at a high rate before the alternator will initiate a charge.


If Tester’s idea does not work then just turn the key on (engine off) and see if the “charge” light lights up on your dash. The field or “excitation” current runs through this light to the alternator on some vehicles.

Missileman beat me to this. I’ll bet he is correct. The bulb may be bad, is making a bad connection in the socket, or there is a problem in the wiring to/from the bulb socket.