ive noticed recently an annoyance. let me set it up.

when im idling [say, stopped at a light], if i push two window buttons [like, if i want to roll down both of the front windows at the same time] -> i feel a vibration come from the back of the car to the front of the car. i can do this on cue, at any time im stopped.

my brother says its causing a misfire because im overloading the alternator [i dont get the connexion]. but it seems to me, with my severely limited experience, that it has to be related to the alternator because its very clearly an electrical issue. or am i mistaken?

[the possibility im mistaken is why this is in general chat instead of electrical]

Simultaneous lowering or raising of two windows will place significant load on the electrical system, but shouldn't have adverse impact. You should be able to operate all four windows at once. I don't understand the vibration that is mentioned though.

The vibration may be caused by the alternator putting more of a load on the drive train as it supplies the power. You could have Autozone/Advance/PartsAmerica test the alternator for free and see if it passes the "stress" or load part of the test.

When your brother says misfire, have you actually seen a misfire from the engine or merely a lowering of the rpms for a moment?

A weak alternator can make a misfire worse, or bad enough to feel it. Not saying that'* your issue, but it can be related.

If the engine stumbles, the exhaust will shake. Your exhuast is a giant tuning fork. The stumble will cause a travelling wave that goes out to the mufflers, and returns.

I think your brother is right, when you load the alternator the voltage drops causing a miss fire. Do you have a voltmeter to see how much the voltage is dropping when you press the windows?

thanks for the replies.

ill check out the voltmeter today.

on a related note, my lights dim very noticeably when i do this.

Don't forget to check the battery condition too. It works with the alternator.

Might check them battery cables for corrosion as well...

Hey Jwak,

Mine does that to. And all my other cars have done this also. I've looked at it as no biggie really. When the lights start dimming bad, then you know its time for a new alternator. IMO anyway.

yeah, im not concerned about the lights dimming. just thought id throw that in.

on my way to work today, i watched the DIC battery reading. reproduced the result, and the DIC dropped from 14.9 volts to 14.0 volts, then jumped right back up. verdict?

As Will said, it can make it worse. It'* worth checking to see if the low voltage didn't uncover a slight existing issue with your plugs/wires/coils. May as well check those, too.