hi everyone

A few days ago I noticed that when I was driving, when I got past 3000rpm, all of my lights would dim; stereos lights, dome lights, headlights and even my fan speed. they would all be at roughly half power. as soon as the rpms went under 3k, everything went back to normal.
the next day it started happening after it when past 2500rpm. and now it is always happening. my fan is at roughly half speed when on max, my headlights are very dim, my stereo light is very dim. when I use the power windows on either side, my stereo goes pretty much blank, then I let go of the power window button, lights come back on, dim but they do come back on.

the car seems to start and run fine. idle is normal, shifting is normal.
any explanations or possible fixes?

I did get a new battery about 2 months ago.

2001 2.4 sunfire, no extras on it, stock stereo, nothing else that should be draining power(I did have a satelitte receiver plugged in my cigarette lighter, but I have removed that with no change to the situation)

thanks in advanced for your help

Clean and tighten battery terminals, ground wire on battery tray and check all conections on back of the alternator, if this checks out then I will have the alternator itself checked.Some auto-parts stores will do it for free.

im not a pro when it comes to electrical issues, but i would guess alternator.. Your battery is only used for starting the car or when the motor is off, then the alt takes over..
Plus its belt-driven so if your problem is effected by RPMs, that sounds like it to me..

But again.. electrical isnt really my thing.. But yeah, i believe alot of places will test your alt for free (or perhaps a small fee) so its an easy first step..

I also agree with checking the ground connection to the frame usually near the starter. Cleaning battery cables is never a bad idea either. I am familiar with electrical on these type of cars and I would definitely suspect the alternator due to the rpm's effecting the problem.

Thanks for your replies

Here is an update:
I did clean the battery terminals to no effect, although i'm sure it did not do any harm either
However I did get my alt tested, and sure enough it was finished.
I was able to get a new one, not a rebuilt, for 170$(Canadian, but its almost the same as US dollar now)
Was that a godo price? I had prices anywhere from 170-500 dollars.

Anyway the new alt worked like a charm. I had to boost the battery at first since it was dead, but after a few minutes, the alternator did its thing
and now the car is running fine Actually even better than before, like lower RPMs at startup and at idle

Thanks for your help!

that'll do it... lol.. and a new alt puts less load on the motor so if yours was bad enough, you'll actually get better fuel economy as well...

170 seems about right for a new one... i normally buy rebuilt but thats a personal choice i guess...