Electrical problem
2002 Ford Focus 4 cyl Two Wheel Drive Automatic 60,000 miles
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the battery light on the dash has recently been coming on while driving my 2002 ford focus wagon. as of today, the light does not turn off. i took the car in to the local mechanic who tested the battery with a voltmeter. the battery is just about one year old. the meter would jump from undercharging to overcharging and sometimes rest in the 'ok' area (sorry, i don't know the numbers). without any further diagnostics i was told it was most certainly a faulty alternator = $300 or so. i am not looking for a cheaper solution, but a firm believer in "measure twice cut once" and want to be certain that all possible troubleshooting is performed before shelling out the bucks.

i have a couple of questions:

1. can they test the alternator before replacing it to be certain it is the alternator that is causing the "jump" of the volts? and, if so, what would one look for when they are testing it to determine it is faulty?
2. does the alternator regulate the volts going to the battery?
3. if not the alternator, what else could cause the volts to jump?

any wisdom would be greatly appreciated.

cat

you can check the alternator with a volts meter
I would suspect bad alternator from your description
but you need and should check battery terminals and alternator terminals and wiring