I've noticed in the past that when the electric fan kicks on that the RPM's drop, but I never really thought much of it. Yesterday when I pulled in my driveway I went to roll up both windows at the same time, once they both reached the top and I was still holding my fingers on the buttons I felt the RPM's drop. I let go and watched the RPM's as I did it again. With both windows already up I pressed both buttons at the same time in the up position I noticed the volts drop and thats normal of course but with the car in park it droped from about 600 rpms to about 400 and was chugging a bit. Is this normal? My car has been running rough lately. The only things I've changed electrical wise are the wires and the coil to MSD, not sure if the new coil would have anything to do with it. Any thoughts on the matter guys?

Mark

 

only thing i can say is you engine does not have the power it used to.....mine drops about 100-150 rpms.

 

The lower the rpm's, the slower the alternator's spinning, so it's not going to be able to make as much power as it does at normal driving rpm's. That said, the power windows are going to affect the car more during idle. However, it's possible your alternator's getting a little weak, a problem which would naturally just get worse at idle. It could also be that your power window motors are starting to get worn out, and drawing too much current. Or it could be both. heh

 

I would change the alternator. That SOB thing failed for me right when I bought my damned car...I had those kinds of problems.

I had a 500 watt amp hooked up to a 12 inch sub with a 1 farad capacitor, and my lights were STILL dimming. Once I got a new alternator there was none of that nonsense. :P

 

Yeah I was gonna say the alternator.

 

Good call guys. I'd take it off and test it first before you cough up $100 for a new one, though.

 

My car does that too.... and my alternator and battery are both less than a year old.

Try turning on your rear defroster. While my power windows do make the RPM's drop, the rear defroster does it even worse. Try it!

Anyway, I think that even with stock pulley's, the alternator does not spin fast enough and it struggles for power/charge. No problems with this while moving right? Chances are, your car is completely normal.

 

Then it could be possible that the altenator is the reason why my car idles rough right? I've replaced darn near everything else wires, plugs, cap & rotor, and MSD coil.