Hello everyone! I have a 2009 Dodge Challenger SE. 3.5L V6. Automatic. The other night while cruising in 4th gear, I noticed a howling/whining noise. Soon as I got to a red light, I put it in neutral and rev'd a few times. Sure enough the whine changed with the RPMS. You can hear it in the video below if you turn your volume up. Also, you'll notice the dash lights dimming with the change in RPMS (beginning of video). I have a brand new Interstate battery (3 weeks old) I pulled into a gas station, popped my hood, and rev'd my engine while recording (1:30 mark). Definitely coming from engine bay. Was a little hard to pinpoint where noise was coming from. Did some research on this forum and it seems similar to what people are experiencing when their alternator is going out. Saw someone with a Charger and their alternator had a whine that changed with RPMS as well, but they were getting a burnt metal smell from their alternator and I think a little smoke? I didn't have any smell or smoke from mine. Next morning whine was pretty loud on cold start (video below). Tried to focus on alternator to see if whine was coming from it. Funny thing is, this time the whine went away after warming the car up for 10min.. Drove it all the way to work (45min commute) with no whining whatsoever. However, it did feel like the car had diminished power and shifted gears kind of late? Just didn't feel as zippy as normal. After work, I immediately drove to Interstate Store (where I bought battery), O'Reilys, & Auto Zone. No whine noise while driving to all three places nor back home. At each place I got my battery & alternator tested. Notes below ~ INTERSTATE: - Used volt meter - Battery 12.8v when car is off - Battery 11.9v - 12.4v when car turned on with all accessories. Not enough voltage to charge battery. It will eventually drain battery. - Car idles at 620RPM, needs to be at least 750RPM to charge battery? O’Reilys - Alternator test - Voltage passed - Diodes failed? AUTO ZONE: - Alternator test - Voltage passed - Diodes failed? - Battery test - Voltage good - Bad battery warning? Could be dead cell? Just bought Interstate battery 3 weeks ago... - Tech said bad battery and alternator? Return/exchange battery? Based on the info I have, I'm going with replacing the alternator. I plan on picking up O'Reilys Ultima or Auto Zone Duralast, remanufactured. Or is new the way to go here..? Before replacing, are there any final tests I can run to confirm it is a bad alternator? If not, any installation tips would be greatly appreciated.. I have the service repair manual instructions and know to get some penetrating spray for alternator bolts. Anyone know if I need to pull radio fuse or use battery tender? I have MyGIG radio. THANKS FOR ALL YOUR HELP!