Pulsing Headlights

[jessica2112]

My headlights "pulse" like get a little dim then brighter, then dim then brighter. It only happens at idle. Like one cycle every 2-3 seconds. Not too severe but just enough to notice it off the car in front of me. I don't see it in the dash lights, just headlights. It's been doing this since I got it. Dealer checked battery and alternator, and both fine. Alternator output regular not pulsing. They couldnt see it during the day. They are not around at night. The pulse is not strong enough to cause my volt needle to show anything. It's steady where it should be. It is beginning to worry me. I don't see it in the tail lights either. What gives? Anyone have this happen to them? 1999 Firebird, no electrical mods. Thanks, Jessica [img]smile.gif[/img]

[hockeyman]

My first guess would have been the alternator. If you had someone check it and it was fine, I'd replace the battery terminal cables and the power cables on the alternator. Something in there isn't allowing the power to flow freely to the headlights.

Do you have alot of corrosion on your terminals?

[jessica2112]

No the terminals are great the car only has 40,000 and underhood everything is as good as new.

[hockeyman]

I'm still guessing the alternator or the voltage regulator inside of the alternator. Is it making any noises like whining, grinding, etc? It doesn't necessarily have to make noises to go bad, but it sometimes does. I've heard people here replacing their alt. at around 20k miles. I have well over that on my 96, and my stock alt. still works great. I guess it just depends on useage, weather conditions, etc.

Sorry I can't offer more advice Good luck though...

[Die Ford V8]

mine did that after i changed the alternator. i would be driving and as soon as i hit 4th gear and lugged my car at all with the headlights on they would dim. my voltage would drop then after i let off my voltage would go up and the headlights get brighter. i took it to an alternator specialist and he said my regulator may be bad. there are a series of diodes in your alternator to rectify it from AC to DC. I have done several tests to check my alternator, but it would never do the bogging thing when they tested it. I had to put it into second gear start and bog it that way with my highbeams on in order to finally get a reading with the problem actually happening.


does your voltage drop when the headlights go dim? check your dash lights also when it is really dark and they mights probably dim a little as well. it might be your alternator, but its kind of a shot in the dark, if you can live with it then do so.

also take a multimeter and put it to your battery and just sit there and watch the voltage. 1 volt could give you the dimming effect and the alternator may be dipping in voltage by letting voltage through the internal diodes(regulator)

my guess is your regulator. if you can rebuild the alternator yourself, i think the diode regulator setup is less than $10. i would go that route, but i also just went through 12 credits worth of electricity classes. [img]tongue.gif[/img] :rolleyes:

i hope this helps in some way.

[Die Ford V8]

if you take your alternator apart(remember how you did so you can put it back together. search online to find a how to. i would just take it apart. and when you go to put it back together you just have to have a pin or something to hold the brushes in while you put rotor assembly back in.) then check your diodes. there are three black things on one side and three on the other. the three one one side will allow current flow one way and not the other. and visa versa with the other three. check with a diode tester by putting the leads up to each one. it should show continuity(allowance of current flow) through one way and give a blank reading the other way.

you obviously have six diodes in all and just one going wrong can cause problems. they are silent and solid state so there are not bearings that can make noice to inticate a bad diode. also if you pull it apart you need to be careful that you put it together EXACTLY the way you took it apart because the placement of the capacitor and wires are critical. make sure the wires of the brushes are also not grounding out against the frame( or at least the one that isnt the ground lead)

one more thing, the diodes cannot be succesfully tested while it is together, and there are three leads that need to be unsoldered. it lookes like a horse shoe and at the bottom of the "U" you will see the three leads that kindof fit into three loops.


i would recommend taking it to an alternator specialist obviously, but do what you want.

[HeadyFirebird'00]

do your lights pulse when you cruise? say 60-90 mph? my lights look like flicker when i going fast, as I pass signs and stuff my headlight figgle and vibrate like crazy... it sucks but its cuz of the light boxes and being flat. less aero dynamit.. thats my theory, i am sure that they dont pulse or dim, but i really looks like they do when im driving.

[CrosX731]

My car does this if I'm cruiseing or acceling.. when I hit the brake thats when my seem to dim by 3% or something like that then come back on. When I test drove a TA WS6 at night I noticed the same deal with that TA. I figure its common in the birds. I others who own them told me that they get that too. You get use to it.

[jessica2112]

Huh, mine is just at idle in drive, stopped WEIRD Guess it was made on Friday, or Monday

[black98V6]

mine did this and eventually the alt went bad, wasn't even putting out 11 volts if I remeber right. I have an optima so luckily I never got stranded. Anyway I replaced the alternator, (that was f'n expensive!) and the problem went away, well I'm now about a year into the new alt and its back to dipping when I am deceling and depress the clutch to let the rpm drop to idle. I get a dim, volts drop and usually come right back up, if sitting at a light for a long time it will suddenly dip, for a second or 2 then come right back up. I was told this happening at idle is normal and it's somekind of internal check the car does to make sure the alt is working properly. *** I have no idea if that is complete BS *** but it's what I have read

[navyblue2000]

mine does that on startup...

heh, my V6 used to die completely! then i'd put it in gear and clutch out and it'd start back up.

Not sure what causes it myself. But mine never affected me adversely. I hope yours doesnt either!

[dafirebird]

I seem to have similar problems. But, in my car, ALL lights flicker. It doesn't matter if I'm driving, or stopped. But, not all the time. Must be possessed¿

[jessica2112]

Last night I turned on the map light on the rear view and it was HORRIBLE! Its spreading..................Jessica

[camaroman1181]

my car has done that for quite a while now.. but only at idle and for a short time after i start up.. it seems to coincide to when the cooling fan kicks on sometimes too, but again only at idle. i think its just teh fan drawing extra current and the car idling not being able to spin the alternator fast enough.. since you have an auto and you say it only happens in drive at idle, your rpms prolly arent high enough to spin the alternator as needed. i really dont think this is a major problem.. maybe a better battery or a new alternator will help. good luck on this one...