MinionBob
Senior Member
- Joined
- Jun 2, 2020
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- Location
- SouthWest
- Your Mercedes
- Viano - 2012 - OM651 Engine - 2.2
This is a post that I hope can help others as fixing electric sliding doors can be a bit of a black art....
Problem: Viano would not lock electric sliding rear doors or the boot. Dashboard error saying LHS door unlocked. Problem was intermittent (and would 'fix' itself with no intervention) but had become worse over the last month to the point where it was pretty much constant.
Fix: New door lock (~£220).
Background/my Findings: There are quite a few parts to the electric sliding doors: Door & pillar contacts, door lock and the electric winding mechanism. Subsequently, diagnosis, at least at a DIY level is awkward as all I can get out of my Icarsoft is that the door is unlocked.
To be clear, in the following, when I talk about locking I don't mean the button going down as is the case when you lock the door via the keyfob; closed might be a better way of describing it but the dash uses the word 'lock' so i'm going to use this nomenclature. Lock basically means detecting that the door is fully and correctly closed.
Door and Pillar contacts were replaced (~£60), mainly as this is a cheap and easy job. No improvement.
Next I turned my attention to the door lock that is located in the rear of the sliding door. Upon removal, the electronic part can be removed from the mechanical part of the lock quite easily. The electronic part comprises a microswitch with a box of sealed electronic gubbins. The gubbins seem to house a solenoid with the flyleads from the microswitch going into the box housing the gubbins, all of which is sealed. The solenoid is the part that physically 'locks' the door for you and (I think) this locking is then detected by the microswitch.
I suspected the microswitch to be faulty as this appears to be the actual part that detects the locked status of the door. It made a nice click, and when tested was consistently working (closed circuit for door open and therefore open circuit for door locked). As a secondary test I put the door lock and electronics back into the door, refitted, but left the microswitch hanging so I could manually activate it ; no change; door would always be detected as door unlocked.
This really left me with three options; wire break somewhere, faulty lock or faulty electric motor. The electric motor is £1k ! so I ruled this out due to cost. I was doubtful about a wire break as the problem would fix itself without any intervention, suggesting that wire continuity is not being changed as would be the case if, say, the vehicle was moved or door opened. This left the lock. Replaced and it fixed the problem.
My instinct is that as the microswitch feeds into the sealed box of electronic gubbins housing a solenoid, the solenoid and switch must communicate with one another. Somehow either the solenoid does not fully or properly actuate, making the vehicle think that the door is unlocked and/or it does not correctly see the status of the microswitch.
The moral of the story is don't rely on the microswitch for diagnosis; there is more to it than that! Phew!
Problem: Viano would not lock electric sliding rear doors or the boot. Dashboard error saying LHS door unlocked. Problem was intermittent (and would 'fix' itself with no intervention) but had become worse over the last month to the point where it was pretty much constant.
Fix: New door lock (~£220).
Background/my Findings: There are quite a few parts to the electric sliding doors: Door & pillar contacts, door lock and the electric winding mechanism. Subsequently, diagnosis, at least at a DIY level is awkward as all I can get out of my Icarsoft is that the door is unlocked.
To be clear, in the following, when I talk about locking I don't mean the button going down as is the case when you lock the door via the keyfob; closed might be a better way of describing it but the dash uses the word 'lock' so i'm going to use this nomenclature. Lock basically means detecting that the door is fully and correctly closed.
Door and Pillar contacts were replaced (~£60), mainly as this is a cheap and easy job. No improvement.
Next I turned my attention to the door lock that is located in the rear of the sliding door. Upon removal, the electronic part can be removed from the mechanical part of the lock quite easily. The electronic part comprises a microswitch with a box of sealed electronic gubbins. The gubbins seem to house a solenoid with the flyleads from the microswitch going into the box housing the gubbins, all of which is sealed. The solenoid is the part that physically 'locks' the door for you and (I think) this locking is then detected by the microswitch.
I suspected the microswitch to be faulty as this appears to be the actual part that detects the locked status of the door. It made a nice click, and when tested was consistently working (closed circuit for door open and therefore open circuit for door locked). As a secondary test I put the door lock and electronics back into the door, refitted, but left the microswitch hanging so I could manually activate it ; no change; door would always be detected as door unlocked.
This really left me with three options; wire break somewhere, faulty lock or faulty electric motor. The electric motor is £1k ! so I ruled this out due to cost. I was doubtful about a wire break as the problem would fix itself without any intervention, suggesting that wire continuity is not being changed as would be the case if, say, the vehicle was moved or door opened. This left the lock. Replaced and it fixed the problem.
My instinct is that as the microswitch feeds into the sealed box of electronic gubbins housing a solenoid, the solenoid and switch must communicate with one another. Somehow either the solenoid does not fully or properly actuate, making the vehicle think that the door is unlocked and/or it does not correctly see the status of the microswitch.
The moral of the story is don't rely on the microswitch for diagnosis; there is more to it than that! Phew!
