Help Wanted! LF & RR Windows Inoperable
 

My driver's window is stuck in the open position following a fairly typical commute home earlier this week. The right rear window is also non operating in the closed position. I checked my CD ROM Benz manual and I don't have a power window elect schematic :mad: I checked the fuse box and I have power to the "b" circuit which is labeled for power windows. It seems strange that both windows on the same circuit would fail at the same time. Any suggestions on where to begin? :confused:

It's one of the fuses I don't remember which one but your car's symptoms is a classic sign of the window fuse. Wiggle them and make sure you've got good contact, it should start working again. If not, replace the fuses. ;)

put in a new fuse to be SURE it's not that.
you can CAREFULLY remove the door panel dieselgiant.com has a nice DIY pictorial on procedure for this.
and you can apply power to the screw leads that power the motor directly to verify it's operation.
john

second that

has to be the fuse

If two windows fail for any reason, there is a one in three chance that they will be on the same fuse.

Mercedes wired the windows so that diagonally opposite ones work from the same fuse. This is probably so that, even if one fuse blows, you can still get one on each side, and one front, one rear, to work.

According to the diagram on the inside of the fuse box cover on my '85 300DT, LF & RR are on fuse "b" and RF & LR are on fuse "a." If even replacing the fuses with new ones doesn't help then you may have a bad switch, relay, or wiring. However, the fuse is always the first to check. Remember the advice previously given: even if you have power at the fuse according to your test meter, replace the fuse with a new one.

Using my DVM, I checked the voltage at the fuse block and I have power on the "b" circuit side of the fuse and the fuse looks fine, visually, so (at least on the surface) it doesn't seem to be the fuse. Unfortunately, I don't have a wiring schematic of the cirucuit since it wasn't included with the CD manual I purchased on the web. I will do the wiggle test and fuse replacement this morning, and go from there. Is the rocker switch difficult to remove from the console? I would like to check it out before tearing into the door.

Thanks to each of you in this forum for all the good advice I recieve :) When I purchased this Benz a year ago, I knew it would involve some tinkering, and this forum is the perfect solution for us DIY's :cool: I don't suppose the Toyota people even have a forum like this do they?

Are you sure about that?

You can pry them out with a small screwdriver.

I'm sure that it's incorrect. I edited the post.

I would rather just remove the wood panel and pop them from the underside so to not mess up the finish on the wood.

Tango. I'm sure about the DVM readings. Let me verify. The power bus seems to be in the center of the fuse block. I checked the opposite side of the fuse for voltage. I'm reading -13.67 volts. This is a "no load" test, so I should perform this while trying to operate the windows, just be sure, which I haven't done yet. Thanks

clean fuse contacts
 

Try this simple fix Before you go pulling switches...
Use some emory or crocus cloth (or superfine sandpaper) to gently but thouroughly clean and polish the fuseholder contacts and the ends of each fuse. Then try it again.

Pull the LH console switch and see if you are getting power at pin 3 (front switch connector).

On the RH rear door switch, check for power to pin 3 & 7.

Also, on the LH front window, does the motor run when "Down" is selected on the switch?

What's the odds of a switch problem if both windows fail to function........at the same time?

I would not bet on a switch problem. Just want to see if power is getting to the switches, since that is an easy place to check.

And. if the motor and the wiring between the switch and the motor is okay, it would be possible to jumper power to the switch connector and get the window up.

Gotcha.........yep.........no power to both switches is my guess.

I pulled the switch blocks from the console and I do have power to both the LF switch (on pins 1,3, and 2) at neutral position and the RR switch (on pins 1, 3, and 2) in neutral position. Does anyone know where I can get a electrical schematic for the power window circuit on line? I think if I had a schematic, I could isolate the problem.

Thanks

On the front switch, the window should go up if you jumper (at the connector) 1 to 4 and 2 to 3. (Down should be 1 to 3 and 2 to 4.)

Tango,

I don't have a pin 4 on the Left Front window. I have the following colored wires going to these pins:
Pin 1-Green
Pin 3-Red
Pin 2-Black
Pin 6-Blue
I believe I reading the pin number markings correctly.

It still seems odd that both windows on the same circuit would fail simulataneously :dizzy2:

That all sounds right, except that you should have a Brown wire at 4 and 5. 4 is ground for the LF window, 5 is ground for the rear window safety switch.

While we are at it, 3 is supply from fuse B, 1 and 2 supply voltage or ground from the switch to motor, depending on switch position. 6 is power for the switch light (LED.)

We are talking about the left front window, correct (the driver's window switch)?

There is no brown wire or Pin 4 on my 1985 300D Cali model. I do appreciate your help. This troubleshooting is not very efficient without a electrical schematic that I can look at so I think I'll wait until my Mercedes mechanic buddy gets back into town tomorrow evening. He has a complete set of factory manuals.
Thanks Again!

Can you verify that you have replaced, not just checked, the "b" fuse. I just had to replace mine, it apparently burned out when I tried to open a frozen shut window. It looked fine, but it had failed. Diagonal window failures are almost always the fuse.

Don't clean the fuses, replace them completely
 

I had a radio and some other problem a while back. Turns out my fuses were just fine .... or so I thought. They were basically all pitted. I was at a repair place one day, the guy told me to replace them right away. A pitted fuse builds up more resistance, and can cause other, bigger electrical problems.

Do yourself a favor. Replace ALL of your fuses with the better, copper fuses. An entire set is like, $9. Buy two so you'll have spares. And if it's not the fuses, then try replacing the switch itself.

jeff 1991 300d, 102k

I have the wiring diagram for your car, but I can't post it because is too big, and if I resize it, you can't read the text. Let me know your e-mail, I will send it to you.

TangoFox and Brian C. and the others:

You guys were right! The window problem was caused by a fuse that was missing just enough metal to show voltage, but not enough to pass current to the windows.

Thanks Again for all your great help on this forum!

I think that's great advice. The aluminum fuses are the source of much trouble. I bought a set of the copper/brass fuses on Ebay a few months ago. One set is enough, as there were plenty of extra fuses for spares.

Good advice on the fuse replacement with copper/brass. Is there any particular supplier or source for locating these improved fuses.

Thanks, Mark from Arizona

Ebay is the least expensive. Do a search for "Mercedes Fuse" and you will find a number of options. Otherwise, http://**************.com/node/48 sells them.

Or even better yet, go to the top of the page and click on "Buy Parts". That's what supports this forum where you found an answer.

Have you looked there for brass/copper fuses?

Well, I went to Buy Parts and the fuse kit has the MB logo on the package. That is what I ordered about 3 years ago and what I received was a container of tinned copper fuses with that same MB logo. Since then, no intermittent fuse problems. (Before that, I had intermittent ACC and windows.)