Symptoms of a bad sport seat module

[bbfulton]

I suspect that I have a bad driver's seat module in my 535is, but I want to make sure that the problem I have is indicative of a module and not a motor or cable.

All the power operations of the seat works fine except for the rear rise and fall control (the height adjustment of the rear part of the seat base). The upward adjustment works fine, but when I press the switch to move it down, there's no movement and I can hear a relay click coming from under the seat. My initial thought was that the internal relay that controls the rear height adjustment has gone bad, but I'm not so sure after checking the wiring diagram and doing a little more testing.

Here's what I'm trying to figure out--
1) If the rear seat height relay had gone bad, wouldn't that prevent both the upward and downward controls from working?
2) If the backdown relay has gone bad, wouldn't that affect the operation of other seat controls that I tested out and all work?
3) Is there any reason to suspect a faulty seat motor given that it works just fine in one direction (i.e. can these motors burn out in one direction but not the other)?

Or am I overthinking this and just need to replace the module?

[Mike W.]

More troubleshooting is in order. The "module" is just a bunch of relays in a box, nothing fancy. And I haven't had it happen on up/down, but on my 535 it would get jammed if I motored the pass seat all the way back. All the way back except for the last half an inch and all was good. I had to take it apart and I forget do what, the seat, not the relay box. Once unjammed, it was fine. I also had to solder a little jumper on a trace on the board inside when a wire got pinched and burned up the trace like a fuse. Easy enough though.

[tn535i]

Have you looked at the ETM at wedophones?
Good questions and I would say

1 Yes, but the same relay provides up/down power... the switch on the other hand triggers the power relay AND the reversing relay for direction
2 not sure what you mean, if everything else will reverse than the reversing relay is OK
3 I don't think so

To me it sounds like a bad diode in the rear up/down circuits. So it energizes the reversing relay but NOT the power or vice versa (thus the click with no motion or click but it is still trying to go up and cannot anymore). Now I don't know if the individual diodes are part of the relays or control module. I suspect the control module but try swapping a couple relays to confirm that. If nothing changes you have a bad control module or really just one bad diode which might not be difficult to replace.

If you can manually turn the motor and bring the rear back down, then try the down button and see if it really goes up then you know there is a bad diode to the reversing relay. If it does nothing then a bad diode to the rear power relay.

[bbfulton]

And I haven't had it happen on up/down, but on my 535 it would get jammed if I motored the pass seat all the way back. All the way back except for the last half an inch and all was good. I had to take it apart and I forget do what, the seat, not the relay box. Once unjammed, it was fine.

Yea, I've heard of certain seat motors jamming up if they've been adjusted to their full range. I THINK that I was pretty close to that for a while before adjusting it the other day, so hopefully that's all there is to it.

To me it sounds like a bad diode in the rear up/down circuits. So it energizes the reversing relay but NOT the power or vice versa (thus the click with no motion or click but it is still trying to go up and cannot anymore). Now I don't know if the individual diodes are part of the relays or control module. I suspect the control module but try swapping a couple relays to confirm that. If nothing changes you have a bad control module or really just one bad diode which might not be difficult to replace.

If you can manually turn the motor and bring the rear back down, then try the down button and see if it really goes up then you know there is a bad diode to the reversing relay. If it does nothing then a bad diode to the rear power relay.

This is along the lines of what I was suspecting. I'll do some testing this weekend and report back.

[jimoreno]

Any update on this?
I'm having problems with my seat back forward movement and I'm suffering the same symptom: clicking but no movement. I'll try a spare controller that I have and if that helps I'll open and check the older one to see if there is a bad diode in it.

Update: replaced my driver's seat module with the one I had and almost everything works now. I've got clicking and no movement from any direction on one of the motors so I guess that one is fried. It's nice to be able to adjust my seat the way I like it!
Question: how the hell do you open the control module? I tried (not forcing it too much) getting a thin flat screwdriver in the center slot but nothing moved. I had forgotten that it was all together with the two motors. I have mixed functions in the passenger seat side. Meaning they work but in the wrong buttons. I did look at the colored dots behind the seat switches to make sure that everything is plugged right where it belongs. Has anyone else experienced this "mixed" functions?

[Oz77]

Here are some pictures of my sports seat passenger side module before I try to repair it. There is a short near the power pin. (DC74 535is).
https://www.flickr.com/gp/197681262@N03/ojqA8o1z67