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Pulse light will light red when pushed.
When attempting to use lumbar, etc, the relays click.
But nothing happens. Besides the relays clicking
These symptoms apply for both seats. Other members suggested looking at a fuse, but since the relays click, I don't think that's the problem.
Both seats move forward, backward, up and down with no problem. Even the switch on top of the seats (that lets you access the rear compartments easier) works fine.
It could be a problem with the pneumatic pump. It's located under the hydraulic pump for the vario roof. It is powered through fuse 54 on the rear panel.
I will have a look. I don't know if this matters from a troubleshooting standpoint, but my trunk auto-close feature still works fine (if the trunk isn't shut all the way, it shuts)
Maybe it has a valve block that is stuck? (similar to how the vario roof pump works)
Maybe it has a valve block that is stuck? (similar to how the vario roof pump works)
I suppose that is possible, but it is far more likely that their is a leak in the pneumatic circuit for the seats.
The PSE system has the ability to diagnose severe leaks in the system. A scan of the PSE control unit with Star Diagnosis or an equivalent may reveal a code for a leak. If a code is set for the seats, I believe operation of the seats is blocked.
Operation can be restored by resetting the code with Star Diagnosis. I believe it can also be restored by removing the fuse which powers the PSE system or disconnecting the Systems battery for a few minutes. The fuse is designated "K40/5f71" and is located in the rear fuse module behind the left seat. Among the row of fuses installed in the module f71 should be a yellow 20-amp fuse in the 3rd or 4th position from the left.
Alternatively, you can check for leaks yourself. The procedure is to unclip each of the vacuum lines from the pump and apply vacuum with a small hand-held pump and monitor loss of vacuum. You can borrow or purchase one of these pumps from an Autozone store.
The pump has circuits for locking the doors, interior, trunk, and fuel filler door, and there are circuits for closing the trunk and operating the multicontour seats. The circuits are labeled on the pump with designations described as follows:
MKL = multi-contour backrest
IZV = interior central locking system
HECK = trunk lid latch
VL = left-hand door lock
VR = right-hand door lock
TD = fuel filler cap
Hmm, if the trunk closer works (and the door locks?), then it's probably not the pump itself. Since it affects both seats, it almost has to be pneumatic because that is the only thing the two have in common. They each have their own control units and are even connected to different SAMs, but they share one pneumatic line coming from the pump. Here is the EPC diagram showing the lines. It isn't specific as to the routing, but the line comes from the pump in the trunk and I suspect runs through the left body wiring channel, under the door sills:
I marked-up the diagram with what a user on another forum named "bayhas" determined on his SL500.
The tee circled in red is evidently in the trunk. The green pneumatic line runs from the trunk into the channel in the right-side rocker panel, and the connector circled in green is in the panel. I presume the yellow pneumatic line runs from the trunk into the left-side rocker panel.
08-10-2016, 05:59 PM
