When you changed the switch did you use a brand new one or a new used one? All these switches get dirty/carbon build up in them. I have removed many of the switches on my car and opened them to clean the contacts. It's an easy DIY and makes a world of difference on how things work.
For what its worth

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1983 300SD
200000miles

I would check the fuse again. The ends of these fuses have a tendency to where off and you lose a good connection. I have had this problem before.
Remove the fuse and take a look at the ends and the clips that hold them in place. I have used a small drill bit to clean the clips that hold the fuse.

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2009 CLS550 55,000
2004 ML350 144,000
2004 X5 95,000
2002 X5 165,000
1996 320S 155,000 (sold)
1991 190E 192,000 (sold)
1989 300SE 160,00 (sold)
1984 300D 210,000 owned since 85, (sold)
1984 300SD 160,000 (sold)

I am having the same problem with my 1983 300CD. I can power it with a jumper from my other car, and the voltage meter shows +14.5 one way, and -14.5 the other way, but hook it up and it will not work! Is that fuse you are speaking of under the hood? If so, what number? If not, where is it?

Hi,

I had a slow AND intermittent sunroof on my 82 300sd.

This is an old thread but maybe my fix can resolve the issue for someone searching for salvation. First I took the headliner off the sunroof and cleaned the gunk off the rails. I cleaned them with acetone. I realized I didn't have the right grease nor did I have my silicone oil bottle (I'm in the middle of a move with some downtime to tinker with the Benz). I decided to leave the rails unlubed since anything I could put on them would prolly goop up eventually. Since I don't use the sunroof often I figured I'd leave it clean till I found the right lube.

Worked better but I decided to pull the cable. Just like the diy tech page...pull little pin, use drive to power out the old cable without punching it through windshield . Pulled it out and cleaned it with acetone. It was gummy. I lubed it with 5w30 oil. I didn't clean the cable shield.

So all was well. It was nice and smooth and I put the headliner back in(the vinyl part on the sunroof, not really the headliner). But the silly roof sometimes wouldn't move. Once it decided to move it moved great. But every five presses, no go. Then I'd press three times or try reversing and it would start moving again.

Saw this thread while searching for answers. I too thought there was a secret relay in there. I theorized I had a burned spot on the motor commutator. I said ok, I'll just pull the motor and scotch bright it a bit and see if that helps. But...then I looked at how the motor was held in. Looked like a lot of work getting it out.

Ok, so I said, maybe he switch was dirty and oxidized after sitting for a decade. The PO told me five years ago that he never opened the roof. It worked but it would stall and he said he was scared he could never close it again. He warned me to never open it. And, so I've never touched it since I got the car.

So I decided to do a lazy mans attempt. I pressed the switch in the open direction 100x with the ignition off. Then I pressed it 100x in the close direction. I tried it with power and it would still not open on every third try. So I pressed it another 200x in each direction. I guess I should have done this while stuck in traffic .

Presto! Sunroof opens and closes reliably with a single press of the switch.

Hope this helps somebody.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles