Falcon45

Hi I am a newbie to the forum since Jan this year so not sure how to use this site.

As a bit of background I have a 15 year old 2001 Y Reg W208 CLK 200 Komp Cabriolet. In my ten years of ownership I have saved £000's on dealer costs by using the MB Forum (thanks guys) and doing all my own repairs including:

1. Changing plastic cog to metal cog in windscreen wiper (design fault);MBD £450, me & Ebay £40
2. Solving windscreen run-off water (design fault); nil cost
3. Replacing heater blower capacitor ruined as result of above; MBD £450, me and Ebay £40
4. Replacing rear wheel reluctors; MBD £1,500, me, Ebay & Indie £300
5. Solving Cam solenoid oil leak; MBD £1,500 to replace wiring loom, US MBDealers General MB recall; Indie £25 to install wiring loom fix recommended on MB Form and me £50 for new O2 sensor ruined by leaking Camshaft solenoid capilarsing oil through wiring loom (about once every 6 months until wiring loom drained through pre cat O2 sensor).

There are too many more to mention but please contact me if you want any more details such as part numbers and costs....10 years DIY experience on this car and still going strong with perefect body and engine after 75,000....it is now only the electric which continually defeat me, hence this post.

The roll bar light switch (S83) blinks until I turn the engine on fully and go through at least one up/down cycle. I have determined that this is probably what is stopping my soft top from working automatically as it also keeps the soft top light switch (S84) permanently lit.

1. FUSES

First thing (simplest) I checked was the fuses...there are 3 fuses related to the soft top operation:
Boot Fuse Block F4 - Fuse 11 - 15A - Provides power to N52 Soft Top controller
Ditto - Fuse 13 - 40A - Powers & protects hydraulic pump motor for soft top
Engine Fuse Block F1 - Fuse 15 - 5A - Also provides power to the ST controller (N52)
These were all OK.

2. Hydraulic Unit Components

Next I checked all the pistons and rods and there are no hydraulic leaks plus the hydraulic reservoir level is normal. The pumps and motors also all seem to be working fine with correct fluid levels and the whole open/close sequences works fine on manual...although red light (S84) never goes out. The Roll Bar/Head Rests also work fine operated through the S83 switch.
Here is a list of all the components checked, their location and their part numbers for other members:
Switchable check valve for manual ops Behind rear seats a 001* OK
Roll bar hydraulic unit (power soft top) Ditto A7/5 001* OK
Hydraulic unit relay Ditto A7/5k1 001* OK
Motor Ditto A7/5m1 001* OK
Power soft top control module Ditto N52 001* ??
Soft top control block (7 connections) Ditto Y56/2 001* OK
There is a good article here in the forums on how to access this and all other ST related units by removing boot carpets and linings and the metal angled panel covering the hydraulic unit...it is honestly not rocket science if I can do it and should only take a few hours to completely strip and then get working...but try not to lose any of the nuts and bolts and cover pins.....about 30-40 in all.:
As none of the fuses or hydraulics seemed to be out of order I then I took it to an Indie who charged me £35 to put it on their star diagnostics and was amazed that it came back with no error codes. We presumed it was simply a faulty switch and that the N52 Soft Top Control Module must be working normally but simply getting a false signal from somewhere...but where?
As far as I can see the only causes I have left to check are the limit switches themselves:

3. SWITCHES

I have tested the following switches with a voltmeter according to the voltages I found in as the MB blogs/forum quote them as the most usual culprits for the N52 soft top controller getting a false signal...
Switch Description Position Part # Qty Status
S83 - RB manual ops & indicator switch UCP to left 1 Blinking Red
S83/5 - RB extended limit switch LHS RB ram to top 1 ?
S83/6 - RB retracted limit switch LHS RB ram to bottom 1 ?
S84 - ST open/close & indicator switch LCP left of gear stick 1 Constant Red
S84/5 - ST compartment cover open switch RHS boot hinge end A 208 820 22 10 1 OK
S84/11 - ST locked limit switch Front passenger roof lock 1 OK
S84/13 - ST open/close train limit switch LHS of A 208 820 24 10 1 OK
S84/15 - ST fabric bow up/down limit switch Under LHS fabric bow towards rear A 208 820 23 10 1 OK
S84/16 - ST bow locked limit switch Under middle of metal bow lock 1 OK
S69/10 - Luggage cover engaged limit switch Luggage cover RHS track end 1 OK
A25S1 - Bow Cover open/closed switch Bow locking point A 129 821 11 51 1 OK
A25S2 - Bow Cover locked switch Bow locking point A 129 821 12 51 1 OK

To be honest, the switches marked OK have only been checked for voltage and resistance at the switch end because I do not have the 126 pin socket box (Part # 129 589 00 21 00) or test cable (part # 104 589 00 63 00) to check the N52 module end in the boot. So I have two questions remaining for the forum:

1. Does anyone know where I could borrow these parts from to check the switches from the N52 end;
2. Alternatively , is there an Indie out there who would be willing to check S83/5 and S83/6 for me and order and replace if necessary?

Falcon45

Just another couple of points on the above as no-one has responded yet:

1. Having just thought that after the roof lock is opened and the windows go down, the next part of the signal process should be a window limit switch to tell the control module N52 that the windows are down before the roll bars are activated. Hence, having diagnosed the toll bar limit switch as the problem, it is perhaps more relevant to check the power windows limit switches first as I have been doing a lot of work on the drivers side window which over and under shoots intermittently when closing.....I had to re-rivet the winder mechanism as the rivets sheered when the window got stuck after and accident about 10 years ago and I have had problems with this window ever since. Unfortunately I cannot see anything on this wonderful thread about window limit switches. Does anyone know the designation and location of these switches....I canot even find which pin they connect to on the N52 module....but surely they must;
2. Is it possible to test all the limit switches by disconnecting the N52 module and applying a voltmeter/ohmeter and auto power probe to the end of the cable disconnected from the module. I have a copy of Chapter 11.5 Cabriolet Soft Top (CST) , Roll Bar (RB) from a MB diagnostic manual I found on a Belgian website (attached) if anyone is interested. It gives all the Diagnostic Test Codes, Switch Locations, N52 pin designations and a complete electrical test program with required values (most of which already appears on this thread in bits and pieces but here it all is in one place).

michael2e

Looking for some quick help related to these limit switches for the soft top. My 1998 SL500 RST holds up mid sequence on opening at point where the tonneau cover raises. I am thinking the limit switch is not working properly (S84/5 - ST compartment cover open switch A 208 820 22 10). Testing with an ohmmeter at the switch itself gives me zero resistance when closed and near zero resistance when open. My question is should the resistance read Infinite when the switch is open? Always a bummer to buy parts you don't need. Thanks!

marko69

You can pull the connector from N52 and check all the micro switch states from the connector end with an ohm meter. Here is a pdf of the connector pinouts and where they connect.
Keep in mind, the picture shows the N52 plug, the connector side will be a mirror image.
michael2e, yes, an open should be infinite ohms.

michael2e

Thanks Marko. Short of digging out N52, the switch in question is readily accessible so I'm just trying to determine if its functioning normally (i.e. open vs. closed) at the source. I understand that this approach doesn't address the wiring or connections. BTW I like your car collection. The others in my stable include an '87 Porsche 951 and '89 Porsche 94 S2. Cheers!

iamtngg

Hello, my rollbar control button don't works, when i push it, it operates passenger door glass. (headrest stays in upper position and i think that's why my soft top stopped working)
+ the glass button does nothing at all. any ideas ? or which module controls this operations ? thanks

CLKGeek

Your N52 connector pinout doc is great, thanks! It is much clearer than some of the WIS images posted here. Where did you get this diagram?