alternator and battery

lukettSeptember 26, 2006

I have a toyota corolla 1998. The question I meet is that when I run a long distance, the battery is dead and I can not start. Some one told me my voltage regulator in the alternator is out of order. It can not stop charging the battery when the battery reaches the highest voltage. Some other people said there is no that function in the regulator. I am confused by them. Any warm-hearted advice can tell me the critical voltage when the regulator stop the charging if it has this function? If I know the voltage alternator stop charging, I can check out wheter mine is good using multimeter. Thanks a lot!

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I'm not a mechanic. I found a simple test you can perform with your volt meter. Hopefully it helps.

One Very Simple Alternator Test:

1) Start Car and run at a normal idle.

2) Connect a Voltmeter Directly Across the battery Terminals.

3) Turn on Headlights to High Beam.

4) check the battery Voltage.
*** The Battery voltage Should read between about 13.8 to 14.2 volts. (Possibly up to 14.5 Volts.)

5) Increase motor speed to about 1500 RPM. The Alternator should now produce a battery voltage between 14.2 and 14.6
*** If it is Lower than 14.2 volts, the Alternator probably has one or more Bad Diodes.

6) Now, Maintain the 1500 RPM and Turn off the Headlights. Run this test for One Full Minute.
"The Battery Voltage should NEVER Exceed about 14.8 Volts".
***If it Does, the Alternators Voltage Regulator is probably Faulty, OVER CHARGING the Battery.

Here is a link that might be useful: Alternator and Battery Test

    Bookmark   September 26, 2006 at 11:40AM
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thank you very much, jasper_60103! I am going to chekc my car.

    Bookmark   September 26, 2006 at 1:08PM
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