My alternator tests 12.5-12.9 volts from a tester at the auto store and shows about the same with my laptop using Freescan. The gauge reads the middle a lot and dip down below it sometimes but always ramdom. The headlights and things don't cause it to go lower. Would this be alternator or battery and what does your voltage read from the scanner? Also what does the scanner read from the computer to get the volts that it shows on my laptop? I am wondering if the cars performance will be affected by a bad battery or alternator and maybe cause an idle issue, starter taking several times, low rpm miss and so on.

 

Voltage sounds a little low it should be charging at least 12.9. I would take the battery out and test that first, if you don't have a charger im pretty sure auto zone does free tests. The cars performance would be affected by a voltage issue, so i would check the battery first since its taking a couple times to turn over. Which means the battery doesn't have enough juice whether its from a bad battery or from an alternator not giving it enough charge.

 

I'd take both the battery and the alternator into AutoZone -- they can test both of them. I think they might both be going bad.

 

A bad coil will do stuff like the driveability issues, change it and see.


Start the car, put a voltmeter directly on the battery(autozone can do this) turn on everything in the car. Lights on High beam, a/c on, blower on high, wipers on high, radio on. The Voltage regualtor should kick up the charge volts. As high as 14 if needed.


If your battery is fully charged the alternator has no need to charge the battery, so it will show 12.9 or so if the voltage regulator is doing its job. But a bad battery will sometimes"fool" the voltage regulator, have the battery load tested.


David