Battery not charging on 1999 Expedition

My battery is not charging on my 1999 Ford Expedition. The battery light flickers on and off in my dash. One service man said I had a bad cell in the battery, no I replaced it with a new one. Batter light continued to flicker. I then pulled the aternator and had it tested at an autoparts store, they said it tested OK but was charing about 1 amp lower than normal. I found a couple of bad fuses in the engine fuse box and replaced them (numbers 1 and 4, 30 amp fuses). Thought that may have fixed the problem, but battery continued to drain until the truck eventually stopped. I'm not a mechanic but thought maybe the voltage regulator might be bad which I undertand is built into the alternator. Could that be the problem??? Would the tester at the auto parts store not pick this up? I'm considering replacing the alternator. Any suggestions???

I would use a DVOM and check the voltage when the vehicle is running it should be around 14.25 volt.
Auto Zone or Advanced should be able to check it in the vehicle. This is at idle with the A-C and lights on.
A good alternator rebuilder can replace the regulator or diodes for you. Advanced wanted $128.00 for a rebuild and the repair shop fixed it for $50.00
on my wifes car.

Rhandwor is right about the alternator. If the light is on when you turn the ignition switch to off the diodes are bad in the alternator. This light will come on when the switch is off because the bad diodes are allowing current to flow from the battery to the alternator which will quickly drain the battery.