Topline Mike

The previous owner of my truck had an alternator in there that had 6 splines, not 7, on the pulley like all the other components (water pump, steering pump, etc.). So it appeared that he just cut off about 1/8 of an inch of the serpentine belt so it would fit the alternator he used. Cobble job. Today I swapped alternators using the one that was on the parts truck that I bought also, and put a new belt on. Well, the darn battery light is now on, but the system is charging. A friend of mine tested this for me. My motor is a 4.6L, the donor truck has a 5.4L in it. The alternators are not exactly the same, but they have the same connections and the two lower bolts match perfectly. Any suggestions with the battery light??

My03fx4

check all the connections, I've seen vehicles come in to the shop plenty of times with a battery light on after somebody else replaced the alternator and didn't fully seat the connectors.

Topline Mike

Thanks for the tip. When connecting the 2 clips, you can a hear the "snap" when they go in. I'll double check them tomorrow. It's brandy old fashioned time now.

Carcrazygts2

It may have a bad diode/regulator. A bad diode/regulator would allow it to still charge but would turn the chrage lamp because the pcm isnt receiving the required voltage