Check your relays early! I just wanted to share my experience is restoring the normal operation of my soft top by methodically eliminating potential troublesome spots.

But first of all, I wish to warmy thank Rudeney and Klaus from Top Hydraulics for the wealth of input they share and also all of you guys that posted your miseries, advices and resolutions that helped me in my own quest.

So, in short, the symptoms: my top wouldn't unlock. Nor resume opening sequence if unlocked manually. But it would happily lock if unlocked manually. Tonneau cover remained shut, did not raise when opening was requested but was strongly pulled down if closing was requested. Note that the usual hydraulic pump whirr wasn't audible when actuating the opening but clearly perceptible when actuating closing. Fluid level is and has always been in the middle mark.

So I went on reading the many related threads, understood the general dynamics of the mechanism and the usual suspects. I printed a copy of Rudeney's diagnostic aid (link here under), watched a few video clips from Top Hydraulics (check their website, it is a wealth of information), grabbed a flashlight and large pack of cold beer and went on troubleshooting the issue. You can read about it in my original thread (link here under).

In summary, soft top trouble can come from 4 sources: switch-related, hydraulic, fuse-related or power-supply related. The resolution is to check methodically all the elements until the problem is found. I first checked what I thought the most obvious suspects: the switches. I stripped the windshield and front bow plastic covers to access the lock cylinder and front locking mechanism. Then checked the rear switches, inspected the various hydraulic cylinders for leaks or obvious sign of damage. The 40A fuse hidden in a box behing the hydraulic pump was also checked for the hell of the discovery. All seemed perfectly operational but still no normal operation of the soft top. Note that only SDS fault reading can ensure 100% exploration of faults. A broken electrical line is hardly visible (Thank you Rudeney for pointing this out).

Finally, I remembered someone mentioning about the 30A pump relays. Those are the yellow cubes on the side of the pump. To remove them, you must first nudge the large connector pinned above them and then pull them out. It is a real challenge for big hands. I used a flat scredriver to nudge them out (I was later told to NEVER use a metal tool to do that). Nothing odd in their appearance (I mean no burn marks etc). Remembering that I could close but not open and that it was mentioned in a thread that one relay is for the opening, the other for closing sequence I decided to switch them to see what happens. And voilą! Normal operation restored.

So my advice is: if the pump doesn't whirr one way (either opening or closing) check first those yellow relays. If the pump doesn't whirr at all (either ways), check first the fuses (the hidden 40A and the dashboard fuse) then the relays to eliminate an easy potential problem there. Swap/replace the relays. They are cheap.

Once you have ruled out a fuse/relay problem, you can go on to check the switches. Note that if fuses or relays are gone, it means that the pump has drawn more current than it should. There is a problem either with the motor or with one or more hydraulic cylinders.

In this picture montage you can see the location of the pump and the two yellow relays on the side. In my case TYCO A 002 542 14 19.



In this process I took an opportunity to clean and oil anything hinging, sliding, locking, pulling or pushing. There is a very interesting video of the front bow cylinder and claws operating the locking and unlocking and switches action in my original thread (link here under).

So, thank you all and wishing you an amazing summer!

Rudeney's diagnostic aid:
http://benzbits.com/w209/soft_top/W2...gnosticAid.pdf

My original related thread with video:
https://mbworld.org/forums/clk-class...-soft-top.html