Battery light ON 93 5.0..new battery/alternator

[fox bodies rule]

the battery red light will stay on until the other side of the light "sees" alternator output voltage = > battery voltage. Based on your "click" comment I would go after a bad ground first but with the light staying on after starting would seem to indicate that you have a problem with the charging output side, so maybe two problems are involved. Fiirst the obbvious. Clean the posts and cables. Get a DVM and check for resistance in the cables and in the connections. With the cables connected to the battery, read from one cable to the other, not the posts. 12.3 to 12.7 is a good indicator of a fully charged battery and little if any resistance in the cable connections to the battery. Did you plug all of the connections back up to the alternator when you changed it out? Has the alternator been bench tested? If not, off to AutoZone, NAPA, Checkers; your choice, for a free alternator output test. If all of your connections and the alternator check out then the fun begins. Check for alternator output voltage getting to the battery by going from the positve post to a known good ground with the engine running and you should be reading anywhere from about 13.2 to 14.5 volts. If not, then back to the begining and find out where you have a bad connection. I hope this helps, it hasn't failed me yet but it has driven me nuts trying to find the problem