This one took me a while to trace, so I thought I'd document it to maybe help others.
Fault - (2009 Fabia 1.2 Hatchback, BBM) Door open light and chime and interior lights coming on at random whilst driving and stationary. Fault was intermittent so made it harder to test.
Summary - Opening and closing each of the doors wasn't conclusive but I thought it was drivers door when I could get the fault to occur. I read up on here and then checked the wiring in A pillar bellows (all looked good unusually), so I then removed the door latch mechanism as described in posts on here. I tested the latch micro switch on the bench and all seemed good. I checked the PCB contacts for the connector and switches both visually and with meter for continuity and all seemed good. I ran 9v from a battery through switch and all good. I then removed the complete door loom (a little fiddly but it can be done without removing the speaker) and double checked all wires - all good. Having not found any problem with door lock mechanism or door loom I decided to put it back together and reinstall without changing micro switches or re-soldering so as not to disturb anything.
I then looked at wiring diagrams in posts on here to see if something else could be happening. It showed that the door latch circuit has two wires (brown, brown/yellow) and when the door is open then these connect in the latch micro switch and earth is supplied to the brown/yellow cable and that feeds back through the bellows to the Convenience unit under the dash. However, there is another brown/yellow cable that goes from the same pin in the bellows connector to the Window Motor/Door Control (not sure why). This meant I could easily test the state of both brown/yellow wires at the window motor connector with the door in operation (have door open all the time and just use a screwdriver to push the door catch cam all the way in to simulate it being closed). Doing this when the connector was off the window motor I was able to see the door catch micro switch always operated perfectly and only completed the earth circuit when the door was open (and the dash light operated correctly). However, when I reconnected the connector to the window motor, that wire was earthed intermittently and caused the dash door open warn light to come on even when door was closed. So I concluded the window motor was incorrectly earthing out the circuit and causing the fault.
As an aside, using this window motor connector (status of brown/yellow wire when unplugged) would be a good way to test the door micro-switch operation without needing to dismantle door catch as easier to get to than the bellows connector and allows window motor to be excluded from the test (as its unplugged).
So I then decided to strip the window motor as couldn't find much info on here. First time stripping it came apart completely and I found a very tiny spot of green corrosion, some metal filings, but not much else so I cleaned and sealed up the pins on the board with PCB varnish thinking it was maybe just moisture or filings causing a short. Reassembled, tested, just the same fault.... So took it off again (three screws, easy), and second stripping it came apart in better way and PCB easier to access. I tested what i could with a meter for continuity of soldered joints behind main connector, but everything else was tiny SMD stuff so beyond me. I didn't find a fault but decided to reflow the solder on the connector joints as they cause issues elsewhere (dash, lock pcb etc). They are small and fiddly, but I got it done and then added PCB varnish on top. Reassembled everything, and everything now works as it should - the original fault of door open light coming on has not happened since.
I did look at replacement window motors before i stripped it and there are many versions, and some are costly, so this might be an option to try before going that route.
The circuit board is small and I couldn't see detail that well (corrosion, joints, filings, etc) so I zoomed in on camera and took lots of photos, then zoomed in again whilst viewing and surprising what can be seen then!
Some pics below, but they are just a fraction of the couple of hundred I must have taken....
Testing the door latch on bench (now know this could have been avoided by testing in situ through the window motor connector)
Model of window motor on this 2009 1.2 hatchback
Window motor connector (brown/yellow at bottom right here is the wire that should be earthed when latch closed (test with connector unplugged from window motor to test latch micro switch first, then plugged in to see if Window motor is providing a false earth).
Connector block on Window Motor PCB, - small amounts of corrosion, but perhaps more under the block itself, but didn't fancy trying to remove.
PCB from Window Motor with my thumb for scale (board is small....) - I reflowed solder on back of connector block (the 14 blobs in the middle - they look a bit domed but connectivity was good and I was concerned at leaving too much heat on the pads with all those SMD's around...) PCB Varnish added on top to seal out any moisture.
Hope that helps someone. I have more pics of dismantling things is required (but there was a 10mb limit on this post).