Dimming Headlights 05 Seirra 5.3

sl33py24 · July 24, 2009

well in the last month i drove on the freeway and it was very bumpy when i've noticed my headlights and dashlight dimming while i was driving and now it does it sometime but it does once and then theirs times when it does it off and on and it looks like am flashing my high beams at ppls..

ive checked the batt and for any lose wires and nothing seem to change the problem

Spurshot · July 24, 2009

If you have another car you can borrow a battery from, swap batteries. Sometimes an internal intermittant short in the battery can cause a problem. It could just as well be something else, but swapping batteries is easy to try.

sleblanc63 · July 24, 2009

I have also noticed my lights seeming to change intensity. I don't recall it being caused by a jarring... but I have noticed it.

stadt11 · July 24, 2009

well in the last month i drove on the freeway and it was very bumpy when i've noticed my headlights and dashlight dimming while i was driving and now it does it sometime but it does once and then theirs times when it does it off and on and it looks like am flashing my high beams at ppls..

ive checked the batt and for any lose wires and nothing seem to change the problem

does your volts change when you notice this? either it's a load on the system, something loose, or bad battery/alternator

Bish · July 24, 2009

My 01 Tahoe did that just before the alternator failed...twice. Once at about 95K and once at about 195K. IIRC it did it for a few months before it started failing to charge.

sl33py24 · July 25, 2009

well sometime i see it below the 14v and other times its passed the 14 but when its dimming it goes up and down a lil bit

Jennabear · July 25, 2009

Do you have an aftermarket stereo system?

06Voy · July 25, 2009

05 tends to do this more cause of the new alternator but I havent seen it happen while driving straight down the road.

sl33py24 · July 26, 2009

I don't have a system in it yet its all stock and I notice that the volt meter at 12 at time when driving and then pass 14.. when the lights are dimming the voltage goes down and up all crazy.. am going to replace the batt cuz it looks like a cheap kind I bought the truck like that and should I get a now alt too while am at it? If so shound I get a hight watt alt or the stock one

brantmacga · August 2, 2009

I have an '05 sierra and its done the same thing since the day I bought it (new).

If I press a window button or locks while the headlights are on, they, along w/ the dash lights, will dim as long as I'm holding the button. Also when my electric fans kick it in high they will dim.

Stex · August 2, 2009

The NBS trucks have an alternator that runs on demand...ie if crusing along not much demand the alternator drops low on volts...then when you compressor kicks on it takes a second for it to gear up thus causing a slight dimming of head lights for a second...

The 05 should not have this?? I would guess battery of alternator...how many miles on current alternator and how old is battery? Also check ground connention, clean even if it looks ok...

WayneNC · August 2, 2009

The 05 Have the (RVC) regulated voltage control.Normal for voltage to go between 12 and 14 volts

motoxxx · August 2, 2009

My 2007 does the same thing...I notice it when I start slowing down the headlights dim a little and then get brighter. I don't have an aftermarket stereo system. Its done that since it was brand new....I've been too lazy to take it in and get it addressed.

sl33py24 · August 2, 2009

just wanted to say thanks for all ur guys help and i did find the problem my alt was going bad.. i replaced it and it went away it does dim when braking and when the fans come on but i can barely tell

stadt11 · August 3, 2009

just wanted to say thanks for all ur guys help and i did find the problem my alt was going bad.. i replaced it and it went away it does dim when braking and when the fans come on but i can barely tell

Do you upgrade your Alt or just replace with the same one?