The battery light came on in my truck about a week & a half ago when my son was driving it. Had the had the alternator replaced last Thursday. Truck was driven about 30 miles on Sunday and about 40 miles Monday with no problems. Then the light came on again this morning (Wednesday) after about 2 miles and while coming to a stop in a parking lot; truck died but restarted. Took it back to the shop but naturally the light didn't come on. The shop tested the battery and it was good. Also test drove it but the only thing they noticed was the radio/clock display dimmed at one point. Any thoughts at all???
1997 F150; ext Cab; 4.6L; 122,000 miles

 

Either your battery is bad (needs to be load tested when nearly fully charged) or the new alt is not up to snuff. I doubt the battery was at a full SOC when tested since most require to be properly charged for a lengthy period of time. I would check the grounds, replace the battery and measure operating voltage.

 

sounds like a bad/ dirty connection

clean ALL of the connections on the batt, alt, grounds (multiple)

i remember having the ground strap for the eng (on my 97) break down on corrode almost to nothing (it's located by the starter)

 

The shop checked the truck out yesterday and it idled rough for them when test driving. They checked things over and diagnosed the problem as having a lot of building up/crud in throttle body, etc. Cleaned it, flow sensor, idle control and everything was fine after that. I had them keep it overnight and try again this morning just to make sure. I picked it up this afternoon and can tell it's idling better than it was. The mechanic said that at very low idle, the air flow probably wasn't adequate enough for the engine to run properly. Just happened to show itself after the alternator was installed for the electrical issue. I'll probably get some fuel system cleaner and run through it occaissionally.

 

Have a 92 f150. When I turn on the lights the y come on for 25 seconds then go off. They stay off for 20 seconds and then come on. Any body have any ideas what is wrong with my truck