Replacing Alternator on 93'

I purchased a 93 Explorer about a month ago and noticed a problem from the start with the Ammeter fluctuating quite a bit. I replaced the battery and cleaned the cables as best I could. Last night about 20 minutes into a 30 minute ride I noticed the Ammeter droping way down to 8 amps and the inside lights and headlights grew progessivly dimm. After a short while the headlights were virtually useless as they provided barely any light. I got home and tried to start the truck after I turned it off and it did nothing. This morning I went out to look at it and it started fine but you could see the Ammeter slowly start to drop. After I put a load on it the Ammeter again dropped down a ways. I only ran it for about a minute. Would this be because of the Alternator? I would like to do this my self and was wondering if there is any kind of trick to replacing one in an explorer. I've been pricing them on line and I see references to 3:00 clock position. Any information would be greatly appreciated.

You can drive it in to one of the local auto parts places and have them test your battery and alternator. That should tell you which one needs to be replaced. You used to be able to just pull the cable off the battery and if it the car still ran, the alternator was good. Not sure about it now with all the electronics on the newer vehicles if this method still works. Also check your belt before you go and replace anything. If the battery is not charging properly, could be a belt issue.

Well battery is brand new. I tested with a pair of voltage testers and I get 12.4 with engine off and 13.0 with engine on without a load. I need to test that under a load. What belts do you mean? The serpentine belt? That belt is in great condition and doesn't appear to slip.

You can also check the voltages on the alternator itself. According to Haynes, with the engine off the B+ terminal should read 12v, the I terminal should have 1v and the A terminal 12v. With engine running at 2000rpm, you should have 14.0-14.7v at the A and B terminals and 13.0-14.0v at the I terminal. Depending on which model you have the I and A terminals may be located on the voltage regulator assy, or on the outside casing of the alternator. The B terminal is on the bottom of the alternator, or the casing. If the voltages are not correct, check the wiring harness. If ok, then you might need a new alternator/regulator.