So I was just about to go out for a bit and on turning the key I got that "rat-a-tat-tat" clicking noise and my voltage is 9.3 . I changed the battery out a couple of weeks ago and well, I'm puzzled. Would the alternator be a good place to start? I was going to change it out anyway in the near future. I'd like to figure this out without having to go to the shop if it might be something simple that I can do at home. What are some other things that could drain my battery? Thanks in advance.

 

Either charge the battery or get a jump to get it started. Then check the charging voltage and see if you have and red alt lights on the panel. You can check the voltage with a DVM or the meter built in the IP. Voltage needs to be around 14 - 14.5 when charging. 12 volts is not going to make it. If you are getting 14 or higher, the alternator is OK.

Not knowing what year car you have makes it that much more harder to give specific information. Please fill out the profile (best) or indicate year car.

Also, has the car been sitting as to why the battery is low?

It just may be the case the battery is bad and won't hold a charge. As far as looking for a current drain, you need to determine the battery is good so you don’t troubleshoot a non-problem.

 

D'oh! Sorry! I have an '89 automatic coupe and it's my daily driver. The only time it sits is from maybe 6 p.m. till the next morning when I go to work, more or less around 5 a.m. Recently though when I was on the road I would have anywhere from 13.5 or 13.6 up into the 14 range on voltage but when sitting at a stop light my voltage would drop into the 12 volt range. I'll check the battery regardless though it was new. Thanks

 

Knowing ones car is important so you have a base line of what is correct for the car. If anything has changed, that is a clue. The charging voltage sounds OK at the higher RPM. But getting down to 12 volts sounds a bit low. My car never drops below 13.9 at an idle with the lights on. But usually is above 14.

Regulators or the diodes in the alternator can produce limited charging capability. They may charge, but not at full current potential. Sounds like what you have but in that gray area.

Possible best is to pull it out and take to get checked to see if it is putting out properly. I would tend to think the new battery is probably good.

 

Unless you have an unusual electrical load, or very low idle rpm, your dash voltmeter should read 14.3 volts engine cold and this will drop to 13.3 volts engine (and alternator) hot. Below 13 volts, the alternator isn't charging the battery and the red battery symbol light on the dash will be lit. I would first charge the battery up with a battery charger! Never leave a lead acid battery sitting discharged! Don't believe that driving the car will charge the battery up and the alternator life is shortened if you do. You may have excessive leakage current and to prove it you need to measure the leakage current by disconnecting the neg batt cable and connecting an ammeter from the neg cable to the batt neg terminal. When the courtesy lights time out, switch your ammeter to lower scales to measure the leakage current. GM says leakage should not exceed 50 milliamps, my 87 draws 27 ma. and I have no problems. Here are some causes of leakage current. At night check for underhood lights, vanity mirror lights, center console light, door panel map lights. Do not leave your ign key in the ign as this keeps the theft alarm on which discharges the battery (why in the heck anyone would do this is way way beyond my understanding). Do you have a radar detector, CB, aftermarket alarm, aftermarket radio, audio amplifier? Check em. If you measure excessive leakage current, you can pull fuses one at a time and watch the ammeter to see if it drops, then that circuit will have to be investigated.