Bad alternator? Bad battery?

[jongreene]

A few days ago I noticed that my lights dim at idle until I give it gas. Theres also a really high pitched whine as if coming from my fuel pump, that gets louder as I rev. Another weird thing was that my once slower than molassis passenger side window was rolling up like a champ! Alternator or battery on the way out?

 

[Lordpaxin]

Get a volt meter and check the voltages.

Too much power usually means alternator problem.

Are your Headlights Noticably brighter.

 

[jongreene]

Well I cant rely on my headlights for any clues, I just got new bulbs so I think theyd be brighter regardless.

 

[91 Turbo Mitsu]

Take a volt meter and check your battery voltage. Then start the car and check the voltage again with it running. At idle you should see anywheres from 13 to 14.5 volts at the battery. If not you may have a bad alternator or a loose belt will cause trouble. Also check your battery terminals to make sure they are clean. Turn on your headlights and check the voltage again. You will see a drop because the headlights are on but it should be above 12.5 or 13 volts. Its hard to test your battery to see if you have a bad cell or low cranking amps. The average battery life from what I have seen at work( I work as a mechanic) in Vermont is 3-5 years. If yours is this old or older you may want to replace it anyways