When my car is on and I do something that requires the use of power, such as putting windows up and down or locking and unlocking the car with the power locks switch, my dash lights and headlights dim, and the RPMs lower slightly. Any idea of what this might be? I have heard that it could be the alternator but I know this is not true because I JUST put a brand new alternator in about a month ago. The guy at the shop did tell me that my battery needs to be replaced sometime in the near future; could it be that? If not, what else could be causing this to happen, because I know this cant be normal. Any help would be appreciated.

 

Your brand new alternator could be defective. Have it tested as well as the battery at one of the auto parts stores.

 

Yea autozone should be able to test out both for free

 

I've just been reading up about the Electrical Load Detector (ELD) which functions as an input to the ECM so it can control voltage from the alternator and provide a steady idle under changing loads. It's located in the fuse box under the hood, and if it malfunctions can produce an error code of 20 from the check engine light. That error code will be different if you get your auto parts store to check your codes, but if it shows up, they can tell you about it. I used the old paperclip in the test terminal to get the flashing code from the check engine light.