Headlights dimming

[EdW]

Mine's done that for eons. It's funny how it's probably been happening and you were just parked a certain way or happened to be looking at a reflection at just the right time and saw the dim when the window hit the stop position. Unless you're noticing other unusual electrical issues, nothing to worry about.

[Chris Tacoma]

*phewwww* I was thinking that maybe the alternator or battery. Seems like a common problem or common thing. It's a 2000 Le that i bought for my wife a couple of weeks ago as a Birthday present. I guess as a thank you I got to drive it the other night I was behind another vehicle at a traffic light when I noticed the lights dim. I was like wtf Wife said she was making sure window was closed all the way.
I feel a little better now knowing it's common. Just got my timing belt kit delivered today along with a water pump and all the seals I need. Hopefully going to get this tackled this weekend.
Thanks everyone for the input

[eurohazard]

After I installed an amp and some subs, I was getting the "dim lights" thing when the bass hit. Of course I could have bought a capacitor to help....but I'm cheap. I removed, and cleaned with a wire brush all the grounds under the hood. Plus I has black wire laying around and terminal lugs, so I doubled up every ground too.

It helped tremendously, but it's not entire eliminated. p.s it's the poor man's ground wire kit.

[Nacmias]

My gen 4.5 does this too with the windows. I also noticed when I have my interior lights on and my hazards, the interior light flickors a little bit. I was going to replace the battery and terminals but I guess I dont have to anymore since this seems like a common small problem.

[Jigg007]

The reason why the lights dim when you roll up the window is; normally when the window is opening or closing, the window and motor are moving all honky-dory like. However, when its fully opened or closed the motor has a 100% work load. (compare it to lifting a 50 pound block to a 400 pound block, you can move the 50 pound block, but you cant budge the 400 pound block, but you try, and you become tired.) So the motor draws its maximum current, Also, the motor will burn out faster. So when the window is done rolling, your done too.

An alternators output is ideally 14.4 volts. But that output is designed to run at 1500+ RPM. so if you're idling at a stop light or parking lot, that output is going to be slightly lower, with less current available, thus light dimming is more prominent.

Another piece, to others that mentioned capacitors, no. Cleaning the terminals (and the extra mile, re-grounding the car) is the best, easiest, cheapest way to improve voltage drops.

[dc_98_cam]

Originally Posted by Jigg007

The reason why the lights dim when you roll up the window is; normally when the window is opening or closing, the window and motor are moving all honky-dory like. However, when its fully opened or closed the motor has a 100% work load. (compare it to lifting a 50 pound block to a 400 pound block, you can move the 50 pound block, but you cant budge the 400 pound block, but you try, and you become tired.) So the motor draws its maximum current, Also, the motor will burn out faster. So when the window is done rolling, your done too.

.... The reason that the window motor uses more current when the window glass hits the upper position stop limit is because the rotor shaft of the window motor becomes locked, and the motor stops turning a small fan blade which is integrally attached to it. ... The current carrying carbon brushes pressing on the motor commutator no longer have adequate cooling ventilation, and become warmer .... Carbon has negative temperature coefficient of resistance .... meaning it's inherent resistance decreases as it gets hotter, unlike copper which increases its resistance when warmer.... Consequently, less resistance in the circuit due to the warm carbon brushes, in combination with the greater locked rotor torque means more current drain on the battery, which can't supply enough current to both the headlights and the locked rotor window motor..... and the headlights get dim.

... Not completely sure about thermal warming effects on carbon brush .... might be a factor.
.... However, what is more likely is that the length of the carbon brushes has eroded due to wear over time .... they are probably much shorter in length than they originally were in the new motors at the factory. As a result, the brushes have decreased significantly in resistance, and are a major factor in the decrease of the window motor circuit resistance, and the primary cause of the battery current drain. ...
Apparently, observing the headlight dimming, this is a major short to ground ... through the carbon brushes and through the motor commutator to ground.
... It is not likely that the cars would have passed quality control when they were new at the factory .... if they dimmed the headlights every time the windows were raised.
... To fix this problem ... suggest replacing the carbon brushes in the motor, or else buying a new motor ... not a used one.

[Jigg007]

Originally Posted by dc_98_cam

.... The reason that the window motor uses more current when the window glass hits the upper position stop limit is because the rotor shaft of the window motor becomes locked, and the motor stops turning a small fan blade which is integrally attached to it. ... The current carrying carbon brushes pressing on the motor commutator no longer have adequate cooling ventilation, and become warmer .... Carbon has negative temperature coefficient of resistance .... meaning it's inherent resistance decreases as it gets hotter, unlike copper which increases its resistance when warmer.... Consequently, less resistance in the circuit due to the warm carbon brushes, in combination with the greater locked rotor torque means more current drain on the battery, which can't supply enough current to both the headlights and the locked rotor window motor..... and the headlights get dim.

... Not completely sure about thermal warming effects on carbon brush .... might be a factor.
.... However, what is more likely is that the length of the carbon brushes has eroded due to wear over time .... they are probably much shorter in length than they originally were in the new motors at the factory. As a result, the brushes have decreased significantly in resistance, and are a major factor in the decrease of the window motor circuit resistance, and the primary cause of the battery current drain. ...
Apparently, observing the headlight dimming, this is a major short to ground ... through the carbon brushes and through the motor commutator to ground.
... It is not likely that the cars would have passed quality control when they were new at the factory .... if they dimmed the headlights every time the windows were raised.
... To fix this problem ... suggest replacing the carbon brushes in the motor, or else buying a new motor ... not a used one.

Holy crap, you win!

[BlueFusion6851]

Damn.... nice explanation.

O/T

So, ChrisTacoma, I just realized you were from MN, Whats shakin?

[dc_98_cam]