As the topic states, i am having some issues with random battery light coming on in my truck. The truck is a 98 f150 xlt 4x4 4.6L. This light will randomly stay off for 2 or 3 days and then come on again. and it can happen at any rpm. I have replaced the battery because it didnt pass the hydrometer test, and also tried putting on a working alternator from another truck that i knew was having no charging issues. and still randomly it would happen. I need some more advise desperately on this one....

 

anyone with any ideas?

 

alternator needs to be replaced... FYI the "battery light" actually has nothing to do with the condition of the battery. It lights up when there is a charging system fault eg.no alt output, A/C voltage detected(bad diode in alternator). To me it sounds like you have a diode starting to fail or you have a brush that is intermitanly losing contact .

 

well thanks for the response....im just really confused because i have tried a new alternator already and the light was still having the same intermittent effect

 

Make sure your alternator is grounded properly. Run an extra wire from the alternator housing to the neg. battery post and see if that takes care of that light comming on

 

If you could connect a digital voltmeter to the battery terminals, perhaps with "jumper leads" so you could put the voltmeter on your dash so you could see it while driving, this would tell you if your battery is, in fact, receiving adequate charging power. I've never trusted idiot lights for much of anything.

- Jack