This question is not really about my car, just in general. I was waiting at a stoplight, waiting for the train to past by. It got stuffy so I decide to roll down my windows. Pressed the button and the windows rolled down and then realize my rpm fluctuate just ever so slightly. Most of the time, it will just slightly dipped down from like 800 or 750rpm to like 700 and then goes back up after you let go of the button (when this happens the interior lights also dim down a little). I was wondering if this was just my car or common among all hondas. Could this be similar to turning your ac on causing the rpm to drop/go up? I haven't tried rolling down the windows at night time to see if my headlights dim also. If it does, then I'm guessing it might be a problem.

 

It happends to me when ever i turn something else on, When i turn on my rear defroster or anything electrical. I haven't had any diming lights though, maybe i just havn't realized.

 

Not only common in Hondas but many other vehicles too, nothing to worry about.

 

The electric load causes the alternator to compensate in turn putting a load on your crank pulley. There is an electric load detector built into the under hood fuse box that senses this and tells your ecu to compensate by increasing the idle. It takes a second and that's why you can tell when your radiator fan comes on. The AC and PS have similar idle up systems. If these are functioning normally then the idle shouldn't dip for more than a second.

 

Oh I see...Wow thanks for the info guys. I'm pretty sure it's common myself.