Disclaimer- again, this may be filed under "stupid questions," so bear with me...

Do your headlights dim when you operate the electric windows? I have been experimenting recently with the various electric things in the car (turning all of them on at once; etc.), but the only devices that can dim the headlights are the window motors. Is this weird, or do I have some sort of problem here?

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Andrew

1989 Volvo 745- 202K

I'm going to say that it doesn't happen in my car and I've got the euro headlights with some pretty nice bulbs....

Its obviously just a momentary strain on the battery\alternator. Its not going to harm your car in any way. Do you see them dim from the inside or have you stood outside while somebody makes it happen to see the effects?

If you're looking from the inside it's probably not really dimming enough to cause any vision impairment, but aside, if you have actually seen the effects of this momentary strain on the system and it impairs driving then you need to definitely do something about it.

I'd just check out your battery to see what kind of voltage its holding and how much you're getting out of the alternator. Just do some experimenting with those two components and you'll figure out the source of the dim.

Good Luck!

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1974 240d "Peace, Love and Empathy" - Kurt Cobain
1982 300sd "It all depends upon the Benz!" - Me
1983 300sd
1985 500sel
1992 300se

Battery has full voltage, and I never get the blinking "low voltage" light out of the defrost switch. There is no impairment- it's just weird to see them dim slightly. Good to know that there is likely nothing amiss.

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Andrew

1989 Volvo 745- 202K

The window motors don't use THAT much power....none of ours dim when using the windows....perhaps your alternator is a bit on the weak side?

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Not on my 83 300D.......

Your description of the battery doesn't help much, what are the voltage readings?

Jim

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14 E250 BlueTEC black. 45k miles
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85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

It's 12.6V when the car is off. The battery is less than a year old. With the car at 1500-2000 RPMs (flaky tach), it stays steady at 13.3ish, sometimes a little higher. The battery is clearly charging, and the voltmeter shows that. The alternator is at least decent from what I've read in the archives. I was just curious to see if this behavior was normal.

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Andrew

1989 Volvo 745- 202K

You may have a weak termination some where. It will be common to both items. Possibly a feeder to the fuse panel.
With the headlights on and someone raising and lowering the window a voltage drop may be found. In fact across any connection if a voltage is read even just with the headlights on. Will probably be the point of abnormal resistance. You may also want to clean up your primary grounds either/or as the voltage drop may be occuring there. It is worth a quick look around if you have a voltmeter and are familiar with its use. Also the grounds should be done as preventative maintenance anyways on an old car. Use a dielectric paste to prevent corrosion after you clean them up.
As someone quoted the window motor in itself is not a heavy load. I cannot offer an opinion on your alternators output. I assume the voltage read was at idle? So it is probably okay but not part of your concern anyways.
A really quick way to check your grounds. Not scientific exactly but of some use. Put a probe from your meter on to the negative battery terminal. Leave the headlights and blower on. The more load the better. Take your other meter probe and touch the valve cover. You should read maybe 1/10 of a volt or less. Take that probe and touch it to a clean area of the body. Again very little if anything should be read if the grounds are in good shape. What you are looking for is any voltage being developed across a marginal ground. It acts as a resistor for all practical purposes and since current is flowing with your heavy load a voltage will be developed if a resistance point is there.
You can also live with your condition if you wish. It may or may not get a little worse with time. Post if you discover anything interesting. It helps us all establish things to watch for as our older buggies age.