How do i know when my alternator is going bad

If the batt light is on, the alternator is not charging the battery.
If the battery won't hold a charge, it could be failing.
If you are having a specific problem with your PT Cruiser or Mustang, let us know what it is.

JUST REPLACED A BAD BATTERY ON MY 2006 FORD ESCAPE IT CHECKED THAT IT HAD A BAD CELL.DROVE IT FOR A FEW DAYS ,NOT VERY FAR OR LONG.THEN WAS DRIVING IN EVENING WITH HEATER,RADIO,LIGHTS WERE ALL ON.WHEN GOT IN TO START IT IT WUDNT SO I JUMPED THE BATTERY.IT TOOK A CHARGE SO I WAS DRIVING HOMW ABOUT 12 MILES FROM WHERE I JUMP STARTED DROVE A FEW MILES AND RADIO QUIT,LITTLE FARTHER LIGHTS WENT OUT BUT DIDNT GET DIM AND WENT OUT JUST WENT OUT BATTERY LITE CAME ON THEN TAILLITES WENT OUT.THEN ALL OF SUDDEN RADIO CAME ON ALL LITES CAME BK ONBUT WAS CLICKING COMING THAT SOUNDED LIKE WHEN BATTERY DOES WHEN WONT START AND NEEDS CHARGE.THEN ABOUT 6 MILES DOWN RD LITES GOT DIM TURN SIGNALS QUIT LOST POWER AND AS I TURNED ONTO A SIDE ROAD VEHICHLE DIED.HAD TO JUMP AGAIN.MADE REST OF 2 MILES TO HOME AND AS TURNED N2 DRIVEWAY DIED AGAIN.SOUNDS LIKE ALT. BUT ALSO WHY WUD LITES GO ON AND OFF LIKE THAT IS IT SOMETHING BESIDES THE ALTERNATOR. CUD IT B SHORTING OUT/