I have a 2007 Aspen with 140K miles. While driving on a short errand today, the battery light came on. When i get home, I turned it off and checked the batter voltage with a voltmeter. It showed about 12.6 volts. I started it again, and checked the batter voltage while it was idling. It started at about 11.9 volts and began dropping until it got down to 11.5 volts, and then stayed at the voltage. The battery is about 2 years old. I live in south Texas, so the temperature today is in the mid 70s. I also noticed kind of a whining or whistling noise coming from under the hood. This noise varies with the speed of the engine. It's not loud, but not something I've heard before. Under the head, it sounds like it's coming from the vicinity of the alternator. Everything else electrical on the vehicle is working fine.

Any suggestions?

 

I forgot to mention, after restarting my Apsen, the battery light did not come back on.

 

I had noise coming from same area and two weeks later my serpentine belt broke on highway . It was a 70$ part but because I was not at home it cost me an extra 300$ for tow and repair at shop. I almost over heated engine,when belt breaks there is no cooling to motor.

 

When I tried to drive the Aspen the following day, I got less than a block from my house and the battery light came on again, followed by all of the warning lights on the dashboard going crazy. I know from experience this is what happens when the battery voltage drops below 10-11 volts. I took the truck back home and when I got it in the garage, I could smell plastic burning. I opened the hood and saw that the connector on the alternator was starting to melt. I slid it away from the alternator, and the alternator was incredibly hot - way too hot to touch.

While I let it cool off, I called around to all of the local part stores to try and locate a replacement. I live in deep south Texas, right on the border - no one had an alternator in stock, and the soonest anyone could get one was 3 days. I called the dealership, he didn't have any rebuilt alternators, which he sells for $160, but he had a brand new one for $485. Way more than I wanted to pay except that I had to leave on a business trip the next morning. I finally called an auto electric shop to see if he had any alternators. He replied he didn't sell them, he just repaired them. He told me to bring the truck in and he could take care of it. Unfortunately, the truck was drivable, so I took the alternator off and took it to his shop.

Anyone that doesn't live in the Rio Grande Valley can't appreciate this tiny shop across the street from the airport. He had alternators of all shapes and sizes stacked everywhere. It looked like a junkyard for alternators. So, this older Mexican gentleman, who doesn't speak a word of English, takes the alternator, checks it with a voltmeter and tells me that it was a dead short internally. He took the cover off and showed me the electronics where all burned up. Going across the room to what looked like a pile of junk, he pulls out the electronic modules, which appeared to brand new, and says he can fix it in less than 2 hours. The electronics looked identical, so I asked him how much he wanted. Now, all of a sudden he speaks English, "$85."

So, I left it with him and went back 2 hours later. He handed me what looked like a brand new alternator and told me it had a 3 month warranty. He had checked the bearings and everything was fine. The noise I was hearing was because of the extreme heat from the alternator.

I purchased a new serpentine belt and put everything back together. It worked perfectly. At the end of the day, I saved $400 vs. buying the brand new part from the dealer.

For anyone replacing the serpentine belt, don't put pass it over the fan blades to install it. That won't work. It has to go underneath the fan hub to be routed.

 

Good info on routing the serp belt.

Be thankful the alternator didn't die on your business trip. I've never had one die near home...it always seems to happen 300 miles from anywhere!!