Author Topic: Windows and RPM loss? (Read 3972 times)

shutter · « **on:** June 20, 2007, 10:22:42 AM »

I have an interesting thing that's been happening, nothing major, but I thought I'd ask around for ideas. Basically, when I roll up the electric windows after parking, it tends to put a draw on the system and RPM's drop under normal idle conditions. It never stalls or anything, but it does drop at least 200 RPMs parked and in neutral. On cold starts, it doesn't do this as much when rolling them down. I assume b/c the idle is bumped up a bit for a cold start. I haven't really played around with them yet under load to see what happens. Any ideas?

Only reason this is bugging me is because recently I've been running a little rich, so I'm looking into freshening up the ignition system some. I'm pretty sure this is an unrelated deal, but maybe not. Interested to hear some thoughts. Also, I'm pretty sure that the slightly rich conditions is that my O2 sensor is on the way out. It's definitely showing it's age, but it tested ok when I bought the car. I'm going to try replacing it first b/c I figured it had a year left when I purchased my baby. It's getting up to a year now.

D. Clay · « **Reply #1 on:** June 20, 2007, 01:49:58 PM »

When the alternator kicks in there is additional drag on the motor. There is no idle increase for this drag like there is with the A/C. 200 RPM is more than normal. It's just barely noticeable normally. I'd check the battery and the alternator first. Then the window motors and mechanism. Sometimes lack of lubrication or dried up grease can put more drag on the motors. I had a problem once with tree sap on the belt moldings that put a drag on the window motors.

bmwman91 · « **Reply #2 on:** June 20, 2007, 02:19:13 PM »

D. Clay is right on. In a clean, free-running mode, each window can pull ~.1hp, and stalled they pull .5hp+! Since it takes very little power to idle, this actually factors in. Just thought I'd toss in some of my findings from the 1-touch window project lol.

gearheadE30 · « **Reply #3 on:** June 20, 2007, 03:40:36 PM »

Interesting numbers bmwman. I had a similar problem, and even the headlights would sap RPM. Turned out the offset on my alternator pulley isn't right and the load is multiplied by the angle. Stupid generic parts

denious · « **Reply #4 on:** June 20, 2007, 06:34:44 PM »

This happened to me too; the right window would go up slower and would drain RPM. In about a week the fuse burnt, so I took the door apart, oiled all the mechanisms for the window, put a new used motor in (which I had for free) and it went back to normal. I guess it doesn't do it when you roll them down cause it must be easier to roll down than to lift...

shutter · « **Reply #5 on:** June 21, 2007, 01:40:31 PM »

Thanks for the responses fellas. I'm sure that you are correct, and relubing everything was towards the top of my to-do list. Hopefully this weekend. I've been cranking on some projects, but no teasers!

My passenger front is struggling as well, and I can tell just from the weather seal at the bottom of the window on that side, that stuff is dry. It seemed to happen about the same time I started running rich, so being an electical deal, I thought I'd throw this out there in the slight chance that they were related. Pretty sure the rich thing is an O2 sensor, but with gas prices I'm not f'ing around!

denious · « **Reply #6 on:** June 22, 2007, 12:21:23 AM »

We are not so different you and I...

My car's running rich too lol, so if the O2 sensor fixes your problem, I'm buying one too!

shutter · « **Reply #7 on:** June 22, 2007, 09:01:21 AM »

I'll probably start looking around for a sensor this weekend or buy one on Monday. I'm basing my diagnosis off of inspecting it 6-8 months ago and inspecting ignition. I'll let you know how it works. At least with gas prices where they are, the price of these sensors is less painful if it gets me out of rich conditions