I've noticed if its really hot or cold outside the roof works fine but when its middling - eg around 18 - 22 degress celsius the boot lid opens and that is as far at it goes. The whirring continues but it wont budge.

Its has always happened from new - all garages failed to fixed to it.
It must be switch related.
Anybody any ideas?

its a 98 SLK.

thanks in advance

 

I've had the same problem. I have a 2002 SLK 32 AMG but the problem is the same. When the temperature reaches 80 - 85 f evrything works except the top won't move. I just use the heel of my hand to nudge the front of the top and it goes down fine. I've thought of having it repaired but it really isn't that annoying.

 

could be the 170 820 07 10 retractable hardtop limit switches above the visors on each side. replace the 170 820 09 10 switch while you are in there. that is the top closed switch and will fail in time.