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I was wondering if anyone else has noticed the headlights dim a decent amount whenever you ask the electrical system to do anything substantial?

I mainly notice it when in my driveway. When I turn the wheel the powersteering pump kicks on, and the lights dim. I also notice it if I'm driving down the freeway and hold any of the window switches up (as in closing a window).

Anyone else notice this? Is the alternator just underpowered on these cars, or is there just something wrong with my car?

Not sure what can be done about it. Would upgrading the big 3 help?
 

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I noticed the same thing recently when the map lights were on, they got dimmer as I was pulling out of my driveway.
 

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noticed it when I was just starting to learn stick and wasn't giving it quite enough gas.
 

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I've also noticed this. I had the same thing on my Honda before I got my new M3. I deemed it normal. The lights didn't dim enough (and the dimming didn't last long enough, just a split second) for me to consider it annoying or problematic.
 

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There probably is no fix, the alternator is not at full output when at or near idle. The power steering pump is a high current draw item same with the power windows. When the windows are up the window motor is seeing more resistance then when moving up and down freely, there for it will draw more current. I can duplicate this on many vehicles, what you describe is normal considering the circumstances you describe. Modern 12V systems are pretty much at the max, there is not much power left to play with. Eventually the automakers will have to switch to a 42V system to deal with the growing electrical load on vehicles and to add even more electrical technology to vehicles.
 

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"...big 3..."

??

Intake, exhaust, ignition?
 

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Discussion Starter #9 (Edited)
There probably is no fix, the alternator is not at full output when at or near idle.
What about in the second case when I am cruising down the highway at 70 mph (~3000 rpm)?

"...big 3..."

??

Intake, exhaust, ignition?
lol, not quite. The big 3 is upgrading the wiring between alternator positive to battery positive, battery negative to chassis, and engine ground to chassis. This just improves the current capability and (I believe) helps the electrical system perform better. It is commonly done when people set up high end aftermarket stereo kits.
 

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I also notice it if I'm driving down the freeway and hold any of the window switches up (as in closing a window).

What about in the second case when I am cruising down the highway at 70 mph (~3000 rpm)?
If the windows are already up when you push the button, then the window motors are asking for max current due to the resistance of the window not being able to go any further.
 

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I don't get it while underway at any speed, but I do notice it when pulling in or out of the garage. I've also noticed that it is worse when the engine is cold. I scratched it up to simply not generating enough current at idle or lugging a bit to power the pumps/HVAC/lights...as was already mentioned.
 

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What about in the second case when I am cruising down the highway at 70 mph (~3000 rpm)?



lol, not quite. The big 3 is upgrading the wiring between alternator positive to battery positive, battery negative to chassis, and engine ground to chassis. This just improves the current capability and (I believe) helps the electrical system perform better. It is commonly done when people set up high end aftermarket stereo kits.
less resistance. Just like water flowing through a hose, the bigger the hose, the more water you can push through without resistance. Amperage works the same way... flowing through your wires pushing voltage. Resistance is found when the wires are too small.... also causing them to get hot (friction).
 

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I had the dimming happen when i first got my 3! But when i bought and installed my HID lights I have noticed no dimming. Obviously i know that the H ID's use less wattage so its a lot smaller load on your alternator! Now if you could replace a bunch of your lights with LED's than you'll def have no problem. If that don't work get a stronger alternator and you def wont see it guarantee!
 

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I don't get it while underway at any speed, but I do notice it when pulling in or out of the garage. I've also noticed that it is worse when the engine is cold. I scratched it up to simply not generating enough current at idle or lugging a bit to power the pumps/HVAC/lights...as was already mentioned.
That's because the battery is the first one to kick in and then its your alternator that finishes up since its recharging your battery so you will obviously see more dimming in the beginning
 

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I had the dimming happen when i first got my 3! But when i bought and installed my HID lights I have noticed no dimming. Obviously i know that the H ID's use less wattage so its a lot smaller load on your alternator! Now if you could replace a bunch of your lights with LED's than you'll def have no problem. If that don't work get a stronger alternator and you def wont see it guarantee!
i would doubt that you would be able to tell when HID's dimmed if they did at all but your probably right. One thing i did notice right off the bat was my headlight/fog light switch was not warm like it use to be when leaving the lights on for awhile.
 
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