The battery came on when I was driving on friday. Then I drove to
shopping with the light on. I could still start the engine when I came back. I test the voltage of battery, it is 12V, but after I start the engine, the voltage drops to 11v, and the light comes on. Is alternator
wrong? Is it easy to replace one by DIY?

fairly easy. get an avr test done. to replace:
1. there are 2 12mm nuts on a braket, remove
2.underneath there is 1 14mm bolt and nut holding the assm there.remove
3. disconnect the power nut (10mm nut on top) and the connecter on the side
4.pull it out.
5.reverse to install
6.to tighten the belt i suggest your wegde a pry bar on alt and get the belt tight and then tighten the 2 12mm nuts.
hope this help. it might be a little off but its basically there.

Thanks.
I look around alterntor. There is a power steering hose above it.
Should I remove the hose too, or it may be hard to pull the alternator out.

fairly easy. get an avr test done. to replace:
1. there are 2 12mm nuts on a braket, remove
2.underneath there is 1 14mm bolt and nut holding the assm there.remove
3. disconnect the power nut (10mm nut on top) and the connecter on the side
4.pull it out.
5.reverse to install
6.to tighten the belt i suggest your wegde a pry bar on alt and get the belt tight and then tighten the 2 12mm nuts.
hope this help. it might be a little off but its basically there.

real quick alternator test, it worked for me: remove the positive wire off of the battery while the car is on, if the engine shuts off then it might be the alternator.

Thanks.
I look around alterntor. There is a power steering hose above it.
Should I remove the hose too, or it may be hard to pull the alternator out.
you jsut gotta pull it out of the holder it is in on the block, just a little hook. if you want you can unbolt the PS pump and put it out of the way, the hose will come it. althought i have never needed to remove the hose.you just wiggle it out.

You can drop the alternator out from the bottom. They have an external regulator......A good rebuild shop in mosy cases will charge you 20 to 30 bucks to rebuild it while you wait. But also check all your connections to see if they are loose or corroded. Baking soda and warm water works great to kill the acid and clean up the mess. Apply grease to any areas that show corrosion to prevent it from coming back. A slipping belt can also be a culprit in not charging. Remember before you attempt to remove it to dis-connect the battery. Good Luck

I started the engine, then disconnected the positive line from the battery, engine was down.

Is there any other reason except alternator?

real quick alternator test, it worked for me: remove the positive wire off of the battery while the car is on, if the engine shuts off then it might be the alternator.

The best way I find is to put a meter on the battery +/- and if the meter is reading 14+ volts, the alternator is charging, if it is reading around 12 volts, your running on battery voltage.

I have found that these cars like to burn out the regulators for some reason, so have your rebuilder check this first before soaking you for a full rebuilt!

Mr.Rob

Lic Mech Auto/Truck/Trailer/Diesel...Ect!