Hello, battery light started to flicker and battery needle jumped up and down while traveling. Stopped at a gas station because needle dropped and head lights started to dim. When I stopped the needle jumped back to the regular position. Advance Auto tested battery and alternator. Alternator tested fine but battery was low. Purchased a new battery and the light would slightly flicker then remain on. Purchased another battery to make it home. Someone told me to unhook my battery post while the truck was still running. If the truck didnt kill that meant the alternator was good. The truck did not kill and battery light is still on without the flicker. I have two large lines that look like battery post that's mounted to the wall. I was told they are fuses but I dont know how to check it. I have no idea where the alternator fuse might be because the owners manual doesnt tell me much.

 

Sorry my signature didn't show in my first post. I have a 97 4x4 EB Expedition

 

There is a small 20amp fuse below and to the right of the fuseable links on the fire wall. It is covered by a black dust cap so you might not see it. Check it out, this migth be your problem.

 

removing the battery cable while running is the worst thing to do. you may have blown the diodes in it.

 

You have a bad Alt. I had same bug and it will eventually kill your battery and later on potentially your starter..
Replace the alternator .. however tip is.. use a direcect OEM replacement.. it will cost you less than an autostore replacement

 

Thank you all for your help. I replaced the alternator and the battery light turned off. Truck ran fine for a while then the truck started running rough. Blue gray smoke started coming from the tail pipe. The thing that tell you how many miles to empty went crazy. Random miles to empty were showing. Noticed gas leaking from under the hood on the ground. Took it to a mechanic and was told my engine computer was spiked. Replaced computer and problem remained. I was told my alarm system was wired to my second fuel injector causing the injector to short. Cut alarm wire to second injector and problem went away. Now I have to go back to the installer who installed the alarm and have them wire it correctly. When it rain it pours.