# Battery light indicator **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [July 16, 2007, 1:51am UTC](https://community.cartalk.com/t/battery-light-indicator/1773 "2007-07-16T01:51:47Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![William\_Palma](https://avatars.discourse-cdn.com/v4/letter/w/eb9ed0/32.png) [@William\_Palma](https://community.cartalk.com/u/William_Palma)\ **Post date:** [July 16, 2007, 1:51am UTC](https://community.cartalk.com/t/battery-light-indicator/1773/1 "2007-07-16T01:51:47Z")
'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? ---
**Author:** ![system](https://global.discourse-cdn.com/cartalk/original/3X/1/d/1d47c66a543aa6c5a7873bb2320858f978ff52ed.png) [@system](https://community.cartalk.com/u/system)\ **Post date:** [July 16, 2007, 2:16am UTC](https://community.cartalk.com/t/battery-light-indicator/1773/2 "2007-07-16T02:16:39Z")
Check the serpentine belt and belt tensioner. ---
**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\ **Post date:** [July 16, 2007, 9:33am UTC](https://community.cartalk.com/t/battery-light-indicator/1773/3 "2007-07-16T09:33:44Z")
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. ---
**Author:** ![system](https://global.discourse-cdn.com/cartalk/original/3X/1/d/1d47c66a543aa6c5a7873bb2320858f978ff52ed.png) [@system](https://community.cartalk.com/u/system)\ **Post date:** [July 16, 2007, 12:24pm UTC](https://community.cartalk.com/t/battery-light-indicator/1773/4 "2007-07-16T12:24:52Z")
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? ---
**Author:** ![William\_Palma](https://avatars.discourse-cdn.com/v4/letter/w/eb9ed0/32.png) [@William\_Palma](https://community.cartalk.com/u/William_Palma)\ **Post date:** [July 16, 2007, 3:59pm UTC](https://community.cartalk.com/t/battery-light-indicator/1773/5 "2007-07-16T15:59:34Z")
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 ---
**Author:** ![system](https://global.discourse-cdn.com/cartalk/original/3X/1/d/1d47c66a543aa6c5a7873bb2320858f978ff52ed.png) [@system](https://community.cartalk.com/u/system)\ **Post date:** [July 16, 2007, 6:21pm UTC](https://community.cartalk.com/t/battery-light-indicator/1773/6 "2007-07-16T18:21:21Z")
Bad diode in new alternator. go back and get another. hopefully still under warranty??? ---
**Author:** ![William\_Palma](https://avatars.discourse-cdn.com/v4/letter/w/eb9ed0/32.png) [@William\_Palma](https://community.cartalk.com/u/William_Palma)\ **Post date:** [July 17, 2007, 1:35am UTC](https://community.cartalk.com/t/battery-light-indicator/1773/7 "2007-07-17T01:35:54Z")
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.