Today in my travels my battery light came on. The alternator gage needle said that is was putting out voltage but a red lite that looked like a battery was on. Twenty miles later it goes off but after next stop I restarted the truck and lite was on again another 40 miles it goes off again. Starts ok everything looks and acts normal any ideas whats going on or while to look ? Just to be safe I parked it outside tonight. A friend of mine caught fire and burned down his building including the truck something electrical ,better safe then sorry I guess.
Mine started doing that recently, right after I replaced the alternator. The sensor that controls that light is pretty sensitive. If it gets just a little out of range, it can trigger the light, before it gets far enough off to show up on the gauge. Get a digital gauge and hook it up to the battery and compare it to when the light comes on. It could be either your alternator getting weak, or a bad sending unit.
Bpogue do you have any idea where sending unit is mounted ?
I have been looking at my 2001 Ford Service CD and have found that it appears that the gauge and warning light are both fed from the same source. There are two wires bringing 12 volts to the light. There is a light green wire with red tracer (wire #904) that goes from the light to the alternator. You will find it in the small connector on the top of the alternator. I believe there are two wires in that harness. The 2nd wire is a white wire with yellow tracer (wire # 1044). It goes to the central junction box (inside cab under dash on driver's side), fuse 29. It should be a 5 amp fuse. The ground for the instrument cluster is a black wire (#57) I'm trying to figure out a way to upload these drawings so you can see how it all lays out.
alternator lite About a month ago I went to look at buying a dump truck about 8 hrs away. I have had no issues before this (except a noise under the hood every now and then, couldnt never trace it) no problem driving up but coming back home about 4pm, the battery lite came on, voltage OK, I decided being I was 5 hrs from home and it would be getting dark soon to stop at a parts store and have it checked out. I took the belt off and the bearing was bad in the alternator. I removed the alternator and got a reman unit and installed it, I took plenty of tools with me in case I needed them for the other truck (which I didnt buy)HUMMM still didnt work, I pulled this alternator and replace it, it still didnt work, pulled the manual out and I guess when the bearing was dragging, I guess it blowed the fuse for the alternator, I dont remember which one, I guess I should have checked it after I replaced it the first time, replaced fuse and its worked great since. Get one of your parts store to put their tester on the truck for you, they dont charge anything for this. I think this was a Auto Zone that I stopped to. Good Luck
After reading all the comments on H.E.F. I just replaced the alternator and it has been fine. Was a very easy fix about 20 minuites to replace , I wonder what they would charge if a fellow would of took it to a dealer ship.The rebuilt alternator cost me $215.00 but will get $65.00 back when I take the core back.