Ok so a few days ago I noticed my 2007 V6 started making a weird whining noise at start up. It seemed to go away once driving. Now today I notice it's constant. I pulled out the OBD2 bluetooth scanner and noticed the voltage was reporting at 11.8 while running. It would bounce to 12.2 when revved.

I pulled out the Fluke and measure 12.2 at the battery while running and 12.6 at the battery while off. To me that indicates the battery is good and the alternator is just not charging.

I already ordered a new alternator and belt from Advance Auto and about to go pick them up. Before I do that what is the likely hood that my tensioner is going bad and the alternator is just not spinning enough? What are the other symptoms of a bad tensioner?

Drove it 2 miles to go pick up the parts...had my radar detector set to display voltage. On the way there it was ~12.9-13V while driving. Made me question my diagnosis...

On the way home the whine was noticeably worse and the voltage readout was 11.1-11.2 while driving. When I pulled in the driveway there was a noticble acrid odor. I thought maybe the rotor siezed and the belt was cooking but everything was still spinning. I guess something went in the alternator. Hopefully I can get it replaced tomorrow before football....I really need it running by Tuesday.

Admittedly, I'm not very knowledgeable about the electrical portion of an alternator. However, I wouldn't imagine that the sound you are hearing could have a huge impact on your voltage. The sound MAY be the alternator pulley bearing going out but as long as the pulley is still spinning I wouldn't expect it to impact voltage.

There's nothing more frustrating than repairing the wrong thing. I had a similar sound that I was certain was the power steering pump pulley. I was so certain that I replaced it and threw an epic fit when it didn't fix my problem. In my case it was one or more of my idler pulleys.

Pull your serpentine belt off and check for play in all of the idler pulleys, the tensioner pulley, the power steering pump pulley, the alternator pulley, and the AC compressor pulley. There shouldn't be any play other than rotational movement. Two of my idler pulleys had a noticeable wobble.

Some people leave the belt on and hit each pulley one-by-one with a spray lubricant. If the sound goes away you found your culprit. That method didn't work for me though.

Good luck.

Well my alternator went out at 141000 miles, since the belt was out and new alternator going in, I spend some extra money and change out the idle pulleys to gates , both upper and one lower was changed, I didn't do the tensioner tho. I also redo my big three upgrade since I had room with the battery out. Good to do if you run some heavy power hungry items.

This oughta answer your questions

http://youtu.be/FTGz0PKIl84

throwing in a bigger alternator, if the only extra power consumer you have is an amp + sub, would it in any way extend your battery life?....am guess a biggger alternator will charge faster,...but does it have any role to play in battery life?
whats the rating of the factory alternator an d the bigger one folks normally install?

It was definitely the alt. Old one came out and measured almost 0 ohms between the case and the terminal. This indicates to me that winding insulation likely failed and is shorting to the case. Put the replacement in along with a new belt and so far it's running great. Running voltage now shows well over 13.5V.

I think factory is 130. I have switched out to a mechman 240amp. Does fine for my needs. 2 Sears pm1 and 3 powerful amps. I think the saying is it's takes power to make power.

So what's the brand of your new alternator? Do you want to rebuild the old one in case the new one craps out? But they have a limited lifetime warranty.

I absolutely had to have my vehicle running by today so I had to go with what was in stock locally on Saturday evening. I ended up getting one from Advance Auto Parts with a lifetime warranty. The alternator was in a CarQuest branded box. I didnt know they were the same company. After core exchange it was $142 for the alt and a new belt. 2 hrs of my time and she is running great again.