# Pulsing headlights **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [January 10, 2009, 7:24am UTC](https://community.cartalk.com/t/pulsing-headlights/24660 "2009-01-10T07:24:19Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![YankeeDave](https://avatars.discourse-cdn.com/v4/letter/y/e36b37/32.png) [@YankeeDave](https://community.cartalk.com/u/YankeeDave)\ **Post date:** [January 10, 2009, 7:24am UTC](https://community.cartalk.com/t/pulsing-headlights/24660/1 "2009-01-10T07:24:19Z")
1998 Nissan Sentra, 1.6L 4cyl Automatic, 107K miles. My headlights, dash and tail lights are pulsing occasionally, at a stead cycle like about 60 per minute. Its not a random flicker but a steady pulse. My mechanic just started looking at it and is going to eliminate possibilities one by one, first by checking the grounds. He put a simple continuity light across the battery posts and saw a visible pulse in its lamp. Another place did a quick check of just the battery and while it had a good charge it indicated that the health was “zero”, meaning real bad. Others have suggested a bad diode in the alternator. So whats going on? ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [January 10, 2009, 11:16am UTC](https://community.cartalk.com/t/pulsing-headlights/24660/2 "2009-01-10T11:16:22Z")
The alternator is about to die, and I would suggest that you replace it before you become stranded when it suddenly stops functioning totally. Also, since you need a new battery, you will quickly kill the new battery if you don’t replace the alternator now. ---
**Author:** ![mcparadise](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mcparadise/32/32_2.png) [@mcparadise](https://community.cartalk.com/u/mcparadise)\ **Post date:** [January 10, 2009, 1:51pm UTC](https://community.cartalk.com/t/pulsing-headlights/24660/3 "2009-01-10T13:51:26Z")
I agree. You need a new alternator and a new battery. Your mechanic should have tested both immediately. ---
**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\ **Post date:** [January 10, 2009, 2:09pm UTC](https://community.cartalk.com/t/pulsing-headlights/24660/4 "2009-01-10T14:09:11Z")
He had the multimeter, and he didn’t check for a/c voltage from the alternator? Added: he used a test light, not a multimeter. You can’t detect a/c with a test light. You can’t do much “mechanicing” without a multimeter, either. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [January 10, 2009, 2:13pm UTC](https://community.cartalk.com/t/pulsing-headlights/24660/5 "2009-01-10T14:13:04Z")
The only thing I can’t figure out is why after having it looked at twice you’re still asking the question. You’ve been told you need a new battery and a new alternator. Simply get them replaced. ---
**Author:** ![golfnut](https://avatars.discourse-cdn.com/v4/letter/g/ad7895/32.png) [@golfnut](https://community.cartalk.com/u/golfnut)\ **Post date:** [January 10, 2009, 2:15pm UTC](https://community.cartalk.com/t/pulsing-headlights/24660/6 "2009-01-10T14:15:15Z")
same thing happen to me. it was diode in alternator. problem solved. good luck