How is this even possible? Were working on a 300cd and non of the windows work at all. We swapped in good known good switches, nothing. I directly power the window motors and they work great. The fuse is fine and I replaced it with a new one and checked continuity. Im not getting any power to the switch sockets though. My question: Is there a relay? Google searches are of no avail neither is alldata.

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1981 300SD 512k OM603

A lot of times the wiring in the door "accordion" get mangled and break over the years. In your case it is just a matter of tracing back the current until you find a break in the wire.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Another thing: They did work about a month ago. I doubt both sides would give out at that accordian and the rear windows dont have a door. The wiring at the switches seems like 20 or 18 gauge which seems a little small which is why Im wondering if there is a relay. On a w123 is there anything between the switches and the windows. What about between the switches and battery (besides the fuse)

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1981 300SD 512k OM603

I don't know but I agree a relay seems likely. Wouldn't it be one of the ice cubes? Try swapping them arround?

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Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/296386-fs-1-owner-83-mb-300d-turbo-rebuild-parts.html

I think some of the silver relays in the fuse box handle windows. Not sure.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

Window fuses are fuse a & b (not number fuses). The window relay is under the plastic box cover on the driver's wheel well top.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

ill try swapping in a good ice cube from my 85

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1981 300SD 512k OM603

It's helpful when you say "the fuse" if you specify which one. There are three associated with the power windows. Do you mean fuses "a" and "b" that control front right\rear left and front left\rear right, respectively? I presume no, since you say "fuse" singular.

So you probably mean fuse 12. This provides power to the relay.

Yes, there's a relay. If Funola knows it's on the wheel well, I'll defer to his experience; but the electrical service manual says it's behind the cluster.

One more question: what's the key position when you're testing? The relay only closes in Run (position II) or start. ACC (position I) doesn't close the relay, so no power to the switches.

To isolate the door wiring, try applying power across pins 3 and 4 on the front switches; or pins 1 and 2 on the rear. Of course there are no rear doors on a CD, so the "mangled accordion" won't be a factor there.

nope. I guess at this point I will start doing continuity everywhere

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1981 300SD 512k OM603

When I said fuse I meant both a and b fuses. I will check no. 12 fuse however I did go through and roll all the fuses and make sure none of them were falling apart but Ill replace it with a new one just in case. I tested those relays on top of the wheel well and I will test the ice cubes behind the cluster next.

Thanks for the information on the pinout for the switches. I was wondering which ones I could apply power.

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1981 300SD 512k OM603

w123 power windows diagram

300D 300CD 300TD power window wiring diagram

Attached Thumbnails

 

I am going by memory from more than a year ago when I last worked on the pwr windows on my 83 300DT. If the FSM says the relay is behind the cluster, then I am clearly wrong and I apoligize.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Oops. Sorry for my mistake. I said it was in the fuse box and I had w126 in mind when I said it, not w123. Apologies for the confusion.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

No slight intended. I added the reference to location behind the cluster in case it wasn't on the fender in order to help the OP with additional troubleshooting info.

I'm citing a 1982 electrical manual I haven't pulled the relay behind the cluster. And the manual isn't perfect - it has 4 pages of errata that correct other errors. My favorite is the correction for the coupe seat back locking diagram: "Seat back locking safety mechanism not shown at all."

Actual BTDT can be more helpful than the book.

Maybe it's time for a "name and locate that relay" thread/sticky. Photos and FSM/BTDT references mandatory.

Now we noticed another issue which I think is related. The car no longer supplies power to the starter relay. I dont think its the NSS. Also this morning the power windows worked momentarily so I'm beginning to think its the main ignition relay or whatever relay energizes when you switch on the ignition and then powers everything else. Is there such a relay in the dash? Possible ignition switch?

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1981 300SD 512k OM603