2003 w208 convertible diagnosis specific questions
short version, fluid level ok, one code for switch plausibility, after clearing, top will open and stow down but cover will not move down to close.
details: snap on Zeus tool is not registering "soft top open" switch state (verified with 2002 w208 comparison car)
back probing (all four) drivers side rear micro switches at the connectors, soft top rocker open / closed, and bow position i get 12V, switching to ground when switch closes. verifying connection to something.
on the 2002 w208, i can manually move the soft top open switch and see it change in data, from "intercept" to "open"
on the 2003, switching the "soft top open" side of the rocker, i measure 0V, but data stays in "intercept" position, not changing to "open"
i traced the 4 wires for both switches and they run forward along the drivers door sill, my diagrams show them direct to the top / rollbar module.
my questions are:
are these two switches connecting to something other then the convertible control module, as they "should" just route to the rear under the back seat?
is there another input / switch i should be looking at (cover is proven,opening/closing when top operates, data stream agrees / reads "open")
side issue, i backprobed the rollbar limit switches, switching 12v to ground as expected, but not changing on data stream (i blame tool software as the functioning 2002 is identical and they both operate as expected)
additionally i don't recall any "U" communication codes, but both an AutoLogic and the latest Matco tablet would not communicate with any modules (i'll blame operator/tool error, but i'm comfortable using both)
I'll provide any additional information requested, and thank you in advance.
The two most common switches that cause an implausible readout in the A208/W208 top system are the black micro switch assembly that is clipped onto the left bow tension cylinder 2088000172 and the micro switch assembly on the rear bow lock. The first one is typically dislodged from the cylinder when it fails to give the proper signal, so you seem to have that one covered already. The latter is not normally the switch itself (unless the steel lever got bumped that pushes onto the switch), but the wiring harness from the rear bow lock to the control module. That wiring harness is routed along the right case cover hinge and it tends to fail where the harness flexes the most while the case cover opens. The two wires can crack or they can short to each other. Unwrap the sheath around those two wires as far down as you can and check for faulty wires.
Hope this helps and good luck!
Klaus
no changes to the bow lock or bow position microswitches, reading unlocked and "up" respectively.
the pump runs continuing to put the soft top in the stowed / open position, after the top open microswitch is grounded, even with pushing down.
without that completion, it does not lower the compartment lid, (case cover?)
it does not set the plausibility code unless you continue holding the open switch until the time out expires.
the case cover opens and closes normally when closing the top, when the bow is in the up position.
there is a wealth of diagnostic material on these forums, specifically Serndipity's links to "stages during soft top (closing) operation" post 16 in this thread
https://mbworld.org/forums/clk-class...-failures.html
i've also used this, very similar issue thread as my template to troubleshoot, even if the stage of operation is different.
https://mbworld.org/forums/clk-class...rt-way-up.html
thread on roll bar and switch states, very to the point, for others viewing:
https://mbworld.org/forums/clk-class...f-problem.html post 17 by Falcon45
i had read most of these posts before my initial post, just wanted them all in one place
i will try to continue this thread with any updates or found resolutions.
thank you.
Last edited by GlennK; May 27, 2021 at 07:23 AM. Reason: added link
confirmed with the top stowed and cover locked, switch flashes and does not attempt to operate.
data says soft top in "intercept" mode rather then "open" but confirms cover and bow locked. (cover is a single microswitch only indicating open position, using the lock microswitch to indicate closed)
i still believe the soft top position switch wiring is going to some place other then N52 soft top / roll bar controller (front center of trunk)
i'm currently seeing if it's an issue with shared data being passed from one module to another.
i fully believe my diagrams are incorrect as the 2 groups of switches are wired to something in the front of the car, impossible to trace manually.
i've traced the wiring to along the drivers door sill, headed forward, and all 4 have 12V present, switched to ground when the respective microswitch are closed.
sorry no resolution yet.
back probing pin 33 12V output to the switch, s84/13a soft top open, showed continuity to ground with switch closed, no change in live data.
as i was absolutely sure none of the other switches were faulty, i pulled the PC board from the car to trace circuits.
pin 33 in yellow goes to the top of a dropping resistor that supplies the 12v (in red) to the micro switch.
it then goes through resistor 104 (100k ohm spec) to the processor chip.
the 104 ohmed out to 5.72m, essentially open circuit, with the ones parallel reading 99.5k
so open circuit between the sense wire to the chip and the switch.
N52 ordered to confirm, no signs of root cause besides single component failure
i'm half tempted to check the dropping resistors to the two roll bar limit switches, as both were not changing in live data on both cars i didn't consider it relevant.
This was not a typical failure, and my confusion is hopefully understandable now.
as there is a core charge to return the module, i won't be checking the roll bar limit switch resistors for a similar issue.
Thank you to all that posted in these forums to help me, and others.


