How do you replace the alternator on a 1999 Chevy S-10 2.2L?

First, disconnect a battery cable, then you have to loosen the belt. The belt tensioner is at the bottom of the engine near the alternator. Put a 3/8" socket in the square hole in it to take the tension from the belt.

The alternator is held in place with three bolts, two of them are on the rear (facing the firewall) and one is at the front. You need a 15mm socket for one of them and a 13mm for the other two. You can reach two of them from the top if you have a small arm that you can get to the back of the alternator. One bolt is hard to see, an inspection mirror is helpful, but you can feel around and find them. There is little room to fit a standard wrench or socket wrench, so it helps to have a 1/4" drive socket wrench or a set of stubby wrenches. The third bolt on the front can be reached from underneath the truck. You do not have a lot of room between the fan and the alternator to get a socket wrench to it.

After removing the three bolts, the alternator will fall out of it's mount, but you will still have difficulty removing it. You first disconnect the wiring harness. The power wire is long enough that you can get the alternator out from the underside and then remove it. The alternator will not reach the ground with the wire attached, but you can set it on a frame member and remove the power wire.

The fan shroud, belt tensioner, some hoses, and wiring get in the way, but you can carefully work the alternator out from underneath the truck, but it is a tight squeeze. It is fairly easy to work the alternator out if you remove the tensioner. There is only one bolt and it is easily accessible for underneath the truck.

One thing to remember when you remonw the bolts from the alternator is to be careful about how much stress you put on the rear bracket! If you let the alternator leverage this bracket it will bend out of place, and it makes it a serious bear to put the new alternator in! I had to do this last night on a 2000 model with the 4 cylinder engine. The key to it is to remove the plastic shrouding around the top of the radiator. There are 3 10 mm head bolts at the front lip and then two more on each side of the fan shroud. Once you get this stuff out of the way (about 10 minutes worth) the accessibility to the Alt is greatly improved. It was not necessary for me to remove the idler pulley. I used a 12 inch bar plus a 10 inch pipe extension for the idler pulley with the 3./8ths drive to rotate the pully and remove the belt. It needs to rotate roughly 90 degrees to fully get out of the way of the belt. On the 2000 model the bracket that holds the alt is cast iron and not subject to being bent. I wrapped a heavy nylon string around the drive pulley and strung it from the hood (held up with prop rod) to keep it from falling. I was able to do all of the work from the top. 1/4 drive ratchets do help given the tight space around the alt. I used a 3/8 drive ratchet to get the 15 mm bolt, the others are 13 mm as noted. Total time for me was about an hour which given it was the first time to do this particular job was not too bad. $120 for a new, not rebuilt alternator

i found this little helpful hint out when i had to do my alternator on my 2002 2.2. there's a little mudflap that folds up right by the inner fender, the thing that keeps stuff out of the engine compartment, and you can see the whole back of the alternator and you can touch all the spark plugs and everything. all you have to do is take the wheel off!!!

Always make it a habit to disconnect the negative side of the battery first and reconnect it last.