alt or battery?

[sdbct1]

Hi gang,
OK here's the problem. When I step on the brakes, close the windows, andthing that requires power my lights dim. At a stop light I idle rough, lights flicker. Is this my alternator, which is origonal, or my battery? Also org. Its a 1997 if I didn't say. Is there something else I should check as well? I'm going long distance in a couple of weeks, don't need to get stuck.

Thanks,
Matt

[toyomoho]

Check battery voltage after it has rested (say overnight) should be about 12.6-12.8V.

Start the car and run at about 2000 RPM with all electrical items off, check voltage at the battery terminals (now with alternator working). Should be around 14-15V.

Increase the load on the alternator by turning on the headlights, heater fan, stepping on brakes. Check voltage again at the same RPM, it should be the same. If it dropped the alternator has a problem.

Also clean the battery terminals. Auto Zone and other stores can do a batter load test and check the alternator (if out of the car).

[joeyicu]

if your alternator was bad your battery light would come on
batteries can become weak, but if the car cranks over nicely and fires up fine then i wouldnt worry about it

my car with the lights on, on the highway at revs, when i roll up windows makes my lights flicker, these alternators probably dont put out that much amperage, thats all

your miss is something else, and it is a horrible idea to diagnose problems just on gut descions and/or guessing, if you are worried about it and are that unsure i would say take it to somewhere knowledgable and see what they say