Ive got a 99 f150 and the charging system doesnt work. ive tried another alternator and had it tested and it is charging fine. my battery light doesnt come on when you turn the key to run. i have no blown fuses. ive tested for a short and it has one but when i pull fuse 15 it stops. fuse 15 has the GEM, RABS, and brake switch on it. and they all test fine. so im pretty confused. any help would be nice

 

What are the symptons? Does it run clean when cranked? Do the headlights dim when running? Or are you just having starter problems?

Could be a bad ground connection.

 

You need to get the battery light circuit repaired, with out it the alt won't charge. My 2002 wiring diagram shows a 40 amp (fuse 111) and a 30 amp (fuse 30) both in that circuit. Basically the circuit goes fuse 111 (battery junction box) to the ign switch and on to fuse 30 (central junction box) to charge indicator and on to terminal 3 of alt (lt grn/red) wire.

Trying to keep it easy to follow; at the alt, the B+ (blk/org) (thats the largest wire) is hot or has 12 volts at all times. The (org/lt blu) goes to fuse 11 (20 amp) also hot at all times. The (lt grn/red) goes to the indicator and should be hot only in start and run. Hope this helps.