[Calmec87]

This sounds very similer to symptoms i've had before. In my case it was the alternator.

As the alternator wears you can almost diagnose it if you have the premium gages, with the battery voltage gage. idle the engine with no systems on, then turn on the blower full blast, head lights, wipers, defrost, operate your power windows, and essentially draw on the electrical system.
A strong alternator should produce enough power that this shouldn't draw to much. if the battery voltage gage drops significantly then you can guess that the alternator might need to be replaced.

If you have the basic gages, you can do the same thing with a voltmeter attached to the battery terminals, but that ussually means someone has to hold it there for you.


And one final thing to note, while my alternator was on its way out, i just left it without repair for a while. this put some stress on the belt. a few weeks after i changed out the alternator, the idler pully went and i threw the belt on my way into work. not an expensive repair, but definitely an inconveniance.