Battery light indicator


'99 Ford Exp. 5.4L 4x4 4 month old alternator. Battery light goes on and off.Seems to go on when I accelerate or when engine is hot.No drop in power when turn on lights/radio/AC.Tested voltage across battery/alternator and all ok.What is going on?


Check the serpentine belt and belt tensioner.


Most auto part stores will check your charging system and battery for free. Most of the time they do a good (not great) job and find the most common problems.


I replaced the serpentine belt the other day but the light came back on. How do I check the tensioner? I also had the battery /alternator checked at two places and the readings were fine. Any other suggestion?


Already changed but light still comes on. How do you check the tensioner is set to proper tension? I have noted the light to come on when the engine is accelerating and usually goes out when the strain on the engine is gone(which is why I suspected the s-belt). The light will also stay on when the engine has been going for awhile(more then an hour). There does not seem to be a drain on the battery, but I also do not want to leave my wife stranded in the middle of the night. HELP


Bad diode in new alternator. go back and get another.
hopefully still under warranty???


Had new alternator placed about four or five months ago. Will the voltage across the alternator show a drop because of a bad diode? If not, is there a way of testing the diode? Greatly appreciate your insight.