Headlights dim utilizing windows - Jeep Renegade Forum
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post #1 of 9 (permalink) Old 07-16-2019, 10:37 PM Thread Starter
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Headlights dim utilizing windows

Just curious if this is normal but headlights and the light on the dash seem to dim when i roll the windows up at night. Curious if this is normal ?
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post #2 of 9 (permalink) Old 07-16-2019, 10:50 PM
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Originally Posted by roxakin View Post
Just curious if this is normal but headlights and the light on the dash seem to dim when i roll the windows up at night. Curious if this is normal ?
This happens to me too. If the windows are up, and I pull up on the switches to make sure everything's closed, they dim too. I also noticed that they dim a little when turning the wheel quickly when moving slow, like in a parking lot.

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post #3 of 9 (permalink) Old 07-17-2019, 05:18 PM
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Here's my theory: the Renegade was designed and built to meet a certain price point. They put in the lowest power alternator they could and geared it with pulleys to make it run as slowly as they could get away with to help fuel efficiency.

So when you are stopped or moving slowly the engine and alternator are also rotating slowly. An alternator's available output power varies in relation to the speed it is rotating. Slow speed = less available electrical power.

The power steering on our Renegades uses an electric motor, and of course, so do the power windows. More electrical loads+slow engine speed = dimming lights.
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post #4 of 9 (permalink) Old 07-17-2019, 10:58 PM Thread Starter
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Ah okay. I was worried about the alternator going bad. It rained heavy today and i had my air condition on to medium and upon acceleration, there was a humming noise. I assume its because i was drawing alot of power as well at night. Kind if regret a bit having such an unreliable car at times
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post #5 of 9 (permalink) Old 07-17-2019, 10:59 PM Thread Starter
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Is the humming from accelerating while driving at night at slow speeds (20) during a rainstorm seem normal? Went away after a bit
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post #6 of 9 (permalink) Old 07-19-2019, 07:37 PM
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Originally Posted by rsanges View Post
Here's my theory: the Renegade was designed and built to meet a certain price point. They put in the lowest power alternator they could and geared it with pulleys to make it run as slowly as they could get away with to help fuel efficiency.

So when you are stopped or moving slowly the engine and alternator are also rotating slowly. An alternator's available output power varies in relation to the speed it is rotating. Slow speed = less available electrical power.

The power steering on our Renegades uses an electric motor, and of course, so do the power windows. More electrical loads+slow engine speed = dimming lights.
I'm not too sure about this. Most alternators are regulated, putting out the same voltage at 2,000 rpm or 20,000 rpm. It's not like at 80 mph it's putting out 14 vdc (made up value) and at 30 it's putting out 10 vdc (also made up value) or something. Modern vehicle computer systems can't handle bouncing voltages. Vehicles travelling consistently at high speed would cook the computers/electrics and those at low speed would have constantly dim lights and dead batteries.

The dimming is due to load on the system, not the spinning speed of the alternator.
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post #7 of 9 (permalink) Old 07-19-2019, 09:21 PM
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As I understand it the voltage is regulated but the current (and therefore power) available is related to speed.
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post #8 of 9 (permalink) Old 07-19-2019, 09:24 PM
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post #9 of 9 (permalink) Old 07-22-2019, 01:31 AM Thread Starter
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So i guess the renegade load isnt much then ?
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