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· Registered
9 Posts
Discussion Starter · #1 ·
im trying to troubleshoot my issue.
i have a 2008 Smart Fortwo and the Power Window buttons and the Side Mirror Adjustment Controller no longer works.
I replaced the whole Master Controller Switch unit but it did not work. (Please view the image below)

I have a Fluke multimeter for help

I have also checked the Power Window fuse. I tested the fuse for continuity and it PASSED. The fuse does not seem to be the issue.

What could be causing the issue?
Could the issue be the motor? But does the motor control both the Power Windows & the Side Mirrors?
Is the issue with the wiring?

any help on what the next steps I should take in the troubleshooting process would be great.

thank you

· Registered
1,585 Posts
Occasionally a wire in the wiring harness or a ground will go bad. I had the same issue with the wire for that turns on the dome light when the door is opened.

There is a large connector that passes all of the wiring from the car to the door located in the front bumper, but you will need to remove or loosen the skin that covers the nose of yours car to access it. From this connector, the wiring harness runs into the door and to the components inside.

In your case, since the power to the mirrors and lights are coming from different fuses (fuse 3 for the windows, fuse 20 for the mirrors), it’s probably a bad ground that they both share. It’s possible that the W43 ground wire is loose, or broken. This ground point is located behind the front bumper, on the left firewall and you will need to remove the nose plastic to access it. The wire color is brown. You should probably do a continuity check from the ground point through the connector and into the door. My guess is the door skin may need to come off too where you may find an open wire. If you are lucky, just the ground point will be loose or broken and you will be able to fix the issue without taking the plastic covering off the outside of the door.

· Administrator
30,158 Posts
Evilution has a wiring diagram for the mirrors (requires a nominal subscription): Evilution - Smart Car Encyclopaedia :)

Also for the windows: Evilution - Smart Car Encyclopaedia

There's also a power window control module under the dash:

N57/2Power window convenience feature control unit

The power window convenience feature control unit is located on the left side below the instrument panel on the crossmember.

The power window convenience feature control unit takes over the control of the side windows. The control unit monitors the power consumption of the connected loads and thereby recognizes lockup or the limit stop of the side window.
The following switches are read in:
Left power window switch (S21/1)
Right power window switch (S21/2)
The following loads are switched:
Left power window motor (M10/3)
Right power window motor (M10/4)

· Registered
1,585 Posts
Congrats on finding the problem. The brown wires are ground connections so it doesn’t surprise me that there were multiple issues on different fuses that were affected.

May I ask where you located the chewed wires? It might give some insight into how to prevent furry friends from getting into my car too!
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