SYSTEM NOT CHARGING

AMP GAUGE SHOW 10 OR ON THE N OF NORMAL,I'VE PUT NEW BATTERY TERMENALS ON, BOUGHT A NEW BATTERY, PUT ON NEW SERPINTINE BELTS, AND REPLACED THE ALTERNATOR WITH A BRAND NEW ONE. WHEN I FIRST START THE VAN THE AMP METER GOES UP TO JUST PAST THE LITTLE PLUS MARK ON THE BATTERY ON THE AMP METER, BUT AFTER ABOUT TEN MINUTES OR SO IT STARTS DROPPING BACK DOWN GRADUALLY TILE IT STOPS ON THE N OF NORMAL ON THE AMP GUAGE.AND REALLY DROPS TO ABOUT 8 VOLTS WHEN I USE THE AIR WITH THE FRONT BLOWER ON HIGH, AND THE HEAD LIGHTS ARE ON. I WOULDN'T DARE TURN ON THE BACK OF THE VANS A/C SYSTEM WITH THE LIGHTS ON. I'M AFRAID IT WILL SHUT OFF THE MOTOR. I CHECKED THE VOLTS ON THE BATTERY BEFORE I STARTED IT (12.56 VOLTS) AND THEN CHECKED IT AGAIN AFTER IT WAS RUNNING,WITH ALL TOYS TO CAUSE A DRAIN ON IT AND IT READ 11.06 AND WHEN I STARTED TURNNIG OFF THE TOYS I WATCHED THE METER,AT FIRST IT TREID SOMETHING CAUSE THE GAUGE WENT UO TO THE NORMAL SPOT FOR AWHILE AND THEN STARTS SLOWLLY DROPPING AGIAN.NOW IT WON'T GO UP IT JUST STAYS AT THE N ON THE NORMAL MARK, IT ONLY MOVES WHEN YOU SHUT OF THE ENGINE.BYE THE WAY THE VAN IS A 1994 FORD AREOSTAR WITH A

3.0 ,REAR WHEEL DRIVE, 90,000 MILES WITH DUAL FACTORY AIR AND ALL THEM LITTLE TOYS USE MEN LIKE. AM/FM/CD/DVD/MONITOR/ PLAYER POWER EVERYTHING ,ABS SYSTEM,BLUE XEONONE HEAD LIGHTS WITH REMOTE CONTROL. RUNNING BOARDS WITH LIGHTS,EXTRA RUNNING LIGHTS, A HOT/COLD/ICEBOX/CONSOLE THAT KEEP BEVERAGES HOT/COLD AND ROOM ENOUGH FOR A HALF CASE OF SOMETHING.AND LAST I HAVE A TV CAMERA IN MY REARVIEW MIRROR THAT TELLS TIME TEMP AND DISTANCE THAT YOU ARE FROM SOMETHING IN COLOR.SO YOU SEE WHY I NEEDS MY CHARGEING SYSTM WORKING CORRECTLY.HAS ANYONE HAD THIS PROBLEM? IT JUST STARTED HAVING PROBLEMS ABOUT A MONTH AGO. EVERYTHING WORKED FINE FOR THE LAST 2 YEARS I'VE HAD IT.