My daughters Fabia (2008) has recently started behaving very strangely.  Below is a quick summary.

 

The alarm started going off randomly (usually at night, and it started during very cold weather).  I replaced the Siren, thinking it was a duff battery.

 

This didn't fix it and after a couple of weeks of locking the car by crawling in the back and pressing the interior door locking switch by the gear stick (to avoid arming the alarm) the door open warning light started coming on whilst driving.  I dug out my old VCDS from my old Audi owning days, and plugged it in to find that  the passenger door though it was open.  Sure enough, the alarm had also been triggered by the passenger door (code 002).

 

On stripping down the door, I found that when I unplugged the cable from the Window Control Module (is that what the window motor is called?) the door warning extinguished and VCDS said the door was closed.  As I had ordered new micro switches for the door mechanism I installed one anyway, and put it all back together again.  Now the strangeness begins!!!!  I plugged in the window control unit and all seemed fine.

 

I rearmed the alarm and it was fine for 12 hours overnight, but suddenly went off in the morning.  At this point I plugged in VCDS and it now  said that the drivers door had set it off.  I stripped the drivers lock and replaced the microswitch and put it all together.  Then the old problem reoccurred where unless I unplugged the passenger window unit the door would not register as closed.

 

So now I have two new microswitches installed, the passenger window controller disconnected and all doors showing as closed.  But the alarm still triggers after a few hours, randomly from the drivers door (which wasn't where the original fault occurred).

 

I have run out of ideas.  Why would the window controller effect the door opening sensor (which works fine without the window controller plugged in, without the window controller plugged in VCDS registers whether the passenger door is open or closed, so the micros switch in the door locks seems to function).  Why would the drivers door suddenly trigger the alarm when the initial problem was with the passenger door?

 

What should I try now?

I should also add, that the only fault code picked up by a scan is 01598 - Drive Battery Voltage.

 

Overnight I put the battery on charge and the alarm still went off in the morning (whilst still on charge), so I don't think it is a low battery problem

The circuits say that the (non-ground) connection from the door open switch goes to both the window regulator unit and the onboard supply control unit. If it's possible try viewing the doors' status (open/closed) in measuring blocks of both J519 (module 09) and J393 (module 46, I think). See if they disagree when the window reg unit is unplugged.

 

I wonder if the fault with the passenger door lock remains, and is actually the ground connection to the lock unit, as I found on one last summer on our mk1, rather than the microswitch itself.

The microswitch wires go into the board at the bottom of the photo and the left hand (ground) one can be seen going to the dodgy joint of the connector.  

 

 

 

 

 

Edited 23 February, 20215 yr by Wino

Thanks for this.  I'll strip it down and have a look at the weekend.  I had just soldered the wires from the new switch onto the wires from the old switch (I hadn't gone into the board).

 

What I can't work out is why the drivers door is now suddenly tripping the alarm.  It all makes no sense!

 

Thanks for your help, much appreciated.

The two window regulator units have a direct data (LIN) connection between themselves, as well as connections back to the central convenience unit (J393). Not sure how that is relevant, if at all; but it might be why the two units seem to 'swap faults'?

 

The logic of the door open switches is such that disconnecting the lock from the window regulator will be the same as the door being closed from its viewpoint. The door-open microswitches short to ground when the door is open, and break the circuit when door is closed.

 

 

 

 

This seems to be a very good answer as our MK2 had this issue and i was in the process of checking the problem out when a very kind soul smashed into the passenger and rear door, car was deemed a write off due to cost of repair,  2 used replacement doors  later 1 rear door with all my parts refitted and 1 front door with window motor switch and door handle refitted and no further problems,  the only part that came from the other car was the door lock and internal wire loom so it does seem the lock was the issue with the alarm and door open light as after these parts were fitted all issues went away strange 

Well, I put a new wiring loom in which had no effect on the problem.  I then replaced the door lock (the one in the car was a non OEM part), and plugged everything back in and locked it.  Overnight it was as good as gold, no alarm went off and I dared to dream it had solved the issu.

 

Then this morning I drove the kids to school and the door open alarm was permanently on again.  VAGcom says the passenger door is open, and the minute I unplug the window control unit in the door the warning goes away.

 

The last thing to replace now is the window control unit (which is just over £200).

 

This is driving me insane!

This was posted very recently, and sounds like it could be relevant: 

 

Thanks for the info.  Reading that is like deja vu.  I did take the window control unit apart as in the thread, and tried to resolder the exact same pins (as they did look a little off colour), but this hasn't helped in my case.

 

I suppose it is the £200 for the control unit (they are very hard to get non-skoda as apparently they are used in lots of VAG cars, but are individually coded to different models).

 

Thanks for the help!

 

 

I could have a go at repairing it if you can be without it for a few days? PM me if interested.

 

Thanks so much for the offer.  I have just got off the phone with Skoda and ordered a new unit out of desperation.  That will have been £500 in total to fix a small problem.  Thanks for all your help