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I was just wondering if it's normal for the headlights to dim a tiny bit when having either the A/C or rear defrost on, or when using power windows.

I don't really notice the dimming on the road, but when parked and the headlights are shining against a wall or similar, I can notice a very slight dimming.

Thanks.

 
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I used to have this problem...
After I upgraded to a 180 amp Ohio Generator alternator, Stinger battery, and 1/0 wiring, no more dimming!!!

 
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Slight dimming is normal/common. Dimming is usually lessened if you upgrade your grounding wires.

 
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Dude its Normal ONLY IF YOU HAVE THE STOCK BATTERY ...

I had the same problem when the compressor turns on ... AND its worst when the bass on ur subs kicks in ...

I switched to an OPTIMA YELLOW TOP ... and all those dimming problem are gone ... even with the most powerful bass !!!!

 
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What you are experiencing is a brief voltage drop. In other words, when you have the car on and all your instruments are drawing power, then you hit the AC or the power windows, youre cars electrical system and computer take a second to bring it back up to what your cr considers a stable voltage. Unfortionatly, it is very normal for most car without an upgraded electrical system. By "electrical system", I mean your car's power plant(alternator)/wiring/battery. I wish it was only a problem of the battery as mani says it is, but replacing the stock one with a starter/deepcycle like a yellow top is like putting a band-aid on a blown off arm. If you have a huge draw on your system, like a big sound system, then you really need to upgrade your alternator, do the "big 3" and upgrade your battery. If you have a smaller to medium sized sound system or you are just worried about dimming lights when you hit the power windows, I would start by upgrading your "big 3" to help with the voltage drops. Realistically though, 90% of the cases of dimming lights when you hit a switch in our civics are just simply a lag of a second or so where the electrical system is just slow to catch up and not a case where your electrical system is unable to supply the need power.

 
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When I upgraded to HID retros, I also upgraded the harness...so now no more dimming.