Issues with recharging 2008 Toyota Yaris

[ItsanEE]

My battery died sometime in the past three days (I use it casually). The weather here has been pretty cold but even last year I didn't have any serious problems starting. No light came on my dashboard last time I used it. Last night I tried to use my car and no lights would power on, my immobilizer light was off and my key would only work manually in the doors. My friend came to give me a boost and when we tried the headlights turned on and the horn blared continuously. Fuses appeared to be intact. The indicator on the battery for battery life should be either red(needs distilled water), blue (okay), or white (needs charging) however it is black. The level is at full so I'm wondering if it's either my battery or alternator. Either way, if I boost it again to take to my mechanic how do I get it to stop blaring the horn? I'm assuming this is related to the immobilizer and that there is some sequence to go through.

Any suggestions?

[CTScott]

Sounds like you have an alarm, as the immobilizer just prevents starting. Try cycling the ignition or door lock to kill the horn.

The battery indicators don't mean much. You should test the battery/alternator by measuring the voltage with the engine off and with it running. If you don't have a multimeter many car parts places will test them for free.

[ItsanEE]

Thanks! Yeah I have a factory alarm as well.

[tmontague]

Sounds like you have an alarm, as the immobilizer just prevents starting. Try cycling the ignition or door lock to kill the horn.

The battery indicators don't mean much. You should test the battery/alternator by measuring the voltage with the engine off and with it running. If you don't have a multimeter many car parts places will test them for free.

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.

[CTScott]

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.