Issues with recharging 2008 Toyota Yaris

[CTScott]

Originally Posted by tmontague

I have a multi meter at home but have yet to need to use it on my car. Care to let me know the steps one would take to test the alternator/batter with the car running and not running? I've always been curious as to how you'd hook the meter up to the car to test electrical components and I haven't found a good explanation online as to how to do this.

Put the meter in voltage DC mode (if it is not autoranging, make sure the range is at least 15-20 V.

Put the red lead on the positive battery terminal and the black on the negative terminal.

At this point with the engine off you are measuring the battery voltage. The voltage should be around 12.5 volts for a good battery. If the voltage is under 11.5 with the car sitting overnight, it may be on its way out.

Now, start the engine and take the same measurement (make sure you are well clear of the fan and drive belt).

With the engine running the alternator is spinning and should be charging the battery. At this point you should be measuring around 13.8 to 14.1 volts (depending on idle RPM). If you are measuring the same or less than before starting the engine, then your alternator is not working. If you measure over 15 volts, then the voltage regulator within the alternator is bad and you may damage the battery or electronics of the car.