Viano / Vito 2012 W639 Electric Sliding Door Lock Issue. Possible Solution

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NotAT5

New Member
Joined
May 17, 2023
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Devon
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Viano 2.2Cdi
Hi All

Thanks for letting me join. So, I’m hoping this note will help others.

I have a 2012 Viano 2.2 CDi with electric sliding doors. My passenger rear electric sliding door has played up since we bought it, as it will shut but won't tell the Vehicle it has locked meaning the central locking won't work on the rear of the vehicle and the vehicle is warning me that the door is open when we are moving.

Using the forum knowledge, I cleaned out the contacts on the doors. And swapped them with the driver’s side. Which didn’t resolve the problem. My door was slightly out of kilter, so using the Youtube video from Mercedes. I have managed to realign it.
This just left the Lock itself. With most people resigning themselves to replace it. Identifying that the microswitch that alerts the vehicle door is closed is at fault.

Looking at the Prices I really didn’t want to be splashing out £260 plus for a new actuator switch.

So out it came!
After disconnecting it from the Car. I can see that the Lock has two micro switches. One for door lock close confirmation and one for the child-lock activation. Also, there is the bare bones lock with cable mechanisms for opening by the: -

Electric in-car button. (Actuator for this on the door panel brace)

Door-mounted handle.

Door-mounted pop-up button.

Also, the lock itself has an actuator under a plastic cover that controls door locking, The door open confirmation microswitch is fed into this actuator.

Now from previous experience with these small DC microswitches, The contacts “fur-up” due to the low current load across them and the DC voltage.

So, the options to fix them in the past have been.

  • Replace it (preferred, not always available at 2:00 am when there are no parts, and the plant is down)
  • Get a big contactor with a juicy AC coil. Or a large DC one. And wire up the microswitch to the Contactor coil. Get it switching that contactor and the current will clean up those contacts for you.
  • Needing a way to defurr the contacts in the switch the other option is to operate the switch several hundred times by hand. Fairly roughly.


Not having options 1 or 2 available to me, I went with 3. You can remove the Microswitch from the lock by prising the material apart above the switch and lifting the Microswitch out. I then spent ages just activating the Microswitch. After a couple of hundred operations. I refitted the micro switch to the lock and rebuilt the lock into the door. After first cleaning out the lock of all debris with brake cleaner and regreasing it.

I was able to test the Microswitch operation by measuring the voltage across the pins in the actuator electrical connector. Please see Electrical Drawing below.

Currently, after many weeks the lock has been working fine. Long may it continue!

Please see the photos below. I'm hoping this will help someone as this door issue has been a constant source of frustration for me.

Door Closed Microswitch.

1684390378148.png





Microswitch next to its mounting point in the lock.

1684390402099.png





Door lock still connected to the Vehicle, Showing the cable connections and the Electrical Connections.

1684390453291.png



Photo showing the door closed micro switch cabling going inside the door lock actuator. This connector covers both the Door lock actuator and the Door closed Microswitch.

1684390509765.png



Below is the pinout for the Actuator and the Door closed micro switch.


Section M14/9 is the actuator and the micro switch. The section above it is the Sliding door contacts.

Looking at M14 the actual Door Microswitch is connected to pins 1 and 3. Pins 5 and 2 are connected to the Lock actuator, showing its current position.

1684390524307.png
 
Thanks for that. Some years ago but I spent some hours looking for a replacement micro switch, and failed.
The next option would be to obtain a old, and maybe even faulty, unit to see if a different type of switch could be fitted.

It's a common issue, and my more used o/s sliding door has just started playing up.

I didn't have the benefit of the wiring diagram, but concluded from testing that 'pads' 3 & 4 of the top pads weren't in use.
-So less ideal but,
disconnecting those in the B pillar, and then linking across from 'pads' 2 & 5 (so terminals 1 & 3 at the mechanism),
and then shorting those pads within the door,
as the door closes the SAM should then see a closed situation, and then permit the 3 rear doors to lock.

Afterthought, a frig across pads 2 & 5 would do the same and be simpler.

So far I've had 2 failed lock situations. Yesterday I cleaned the pads, and that may have resolved my problem?? If / when it plays up again I'll try my frig and let you know.
 
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Thanks for that. Some years ago but I spent some hours looking for a replacement micro switch, and failed.
The next option would be to obtain a old, and maybe even faulty, unit to see if a different type of switch could be fitted.

It's a common issue, and my more used o/s sliding door has just started playing up.

I didn't have the benefit of the wiring diagram, but concluded from testing that 'pads' 3 & 4 of the top pads weren't in use.
-So less ideal but,
disconnecting those in the B pillar, and then linking across from 'pads' 2 & 5 (so terminals 1 & 3 at the mechanism),
and then shorting those pads within the door,
as the door closes the SAM should then see a closed situation, and then permit the 3 rear doors to lock.

Afterthought, a frig across pads 2 & 5 would do the same and be simpler.

So far I've had 2 failed lock situations. Yesterday I cleaned the pads, and that may have resolved my problem?? If / when it plays up again I'll try my frig and let you know.
Hi M80 I had no luck with the contact pads, even after cleaning and swapping. I read somewhere that shorting terminals 1 and 3 causes the SAM to think the door is shut as soon as it goes to close. which can cause its own issues. Can't remember the exact details of the problems this causes. But potentially it could try to lock before the door had shut?

The cost of the complete lock is frustratingly high when it's only a tiny microswitch causing the issue.

Good luck, I would be interested to know if it works.
 
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NotAT5

The cleaning of the pads and the lock working is very possibly just coincidental, that the switch decided to make.


The cleaning of the pads and the lock working is very likely just coincidental, that the switch then decided to make.
I'm seeing 2nd hand locks that are silly prices, especially as it is likely the micro switch on those will give up soon enough. As so many of these vehicles were previously taxis the locks will have been well used.

From what you say it is very possible that the SAM needs to see the micro switch o/c as it closes, then the lock closes the micro switch on closure. So my frig wouldn't work, it would need to be another switch in parallel somewhere. That feels like too much faff to have to change the state of that switch each time the door is used.
I can see a way of creating that condition using the unused pads of 3 & 4 (and a delay cct), but in truth I think I would just spend the dosh on a new lock, that should be good till my Viano is no longer.

I have read of others replacing these locks, it was a while ago and I seem to remember the price being less than £150. Their old lock would be so useful now, perhaps.
 
Mine has failed to see the door locked a few more times, it might if i open and close again but not reliably.

I've ordered a new lock from Poland, being as I don't want to be stuck remote, loaded, and unable to lock the 3 rear doors.

Meanwhile I see Star (well Dab) has very little activations for the electric side doors.
What can be done is to clear any codes,
denormalize,
then normalize with and open / close / open procedure.

Chances are it'll make no difference as the micro switch is merely o/c or c/c, and this is likely just for setting up the limits of travel. But I'll report back anyway.

The other issue with these electric doors, is they forgetting that they are electric.
I blame that on a low battery voltage after being stood for a while, and the load shed locking them out and forgetting to restore them when voltage is restored. The electric heated seats do this but restore them soon after a start.
For this I pull the fuse/s in the under bonnet fuse box, the door/s are then restored. On F34 fuse tray that's fuses 27 and 28 (30 amp).
 

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So the part arrived a few minutes ago.
Advertised as brand new and unopened, it is not.
Complete with many scratches, and damage to the connector it is clearly from a broken vehicle.

It being pre used it certainly isn't worth fitting as it could be already knackered, or close to being. Even if it tested as ok now it shouldn't be trusted to remain that way for long.

It is via ebay so I shall start a case.
£152.95 for item.
£24 postage.
£47.67 to DHL yesterday for customs charges.

This is the 1st time I've had to deal with a return to the EU, and tbh I'm not looking forward to the required process to recover such as VAT.

That'll teach me for not buying from the UK, although I couldn't see one available here.
So now I guess it's off to a main dealer, and wait.
 
So the part arrived a few minutes ago.
Advertised as brand new and unopened, it is not.
Complete with many scratches, and damage to the connector it is clearly from a broken vehicle.

It being pre used it certainly isn't worth fitting as it could be already knackered, or close to being. Even if it tested as ok now it shouldn't be trusted to remain that way for long.

It is via ebay so I shall start a case.
£152.95 for item.
£24 postage.
£47.67 to DHL yesterday for customs charges.

This is the 1st time I've had to deal with a return to the EU, and tbh I'm not looking forward to the required process to recover such as VAT.

That'll teach me for not buying from the UK, although I couldn't see one available here.
So now I guess it's off to a main dealer, and wait.
Did you find a solution to this other than replacing the lock mechanism? I have the same problem intermittently and don’t really want to spend big bucks on the solution. Tx
 
Hi All

Thanks for letting me join. So, I’m hoping this note will help others.

I have a 2012 Viano 2.2 CDi with electric sliding doors. My passenger rear electric sliding door has played up since we bought it, as it will shut but won't tell the Vehicle it has locked meaning the central locking won't work on the rear of the vehicle and the vehicle is warning me that the door is open when we are moving.

Using the forum knowledge, I cleaned out the contacts on the doors. And swapped them with the driver’s side. Which didn’t resolve the problem. My door was slightly out of kilter, so using the Youtube video from Mercedes. I have managed to realign it.
This just left the Lock itself. With most people resigning themselves to replace it. Identifying that the microswitch that alerts the vehicle door is closed is at fault.

Looking at the Prices I really didn’t want to be splashing out £260 plus for a new actuator switch.

So out it came!
After disconnecting it from the Car. I can see that the Lock has two micro switches. One for door lock close confirmation and one for the child-lock activation. Also, there is the bare bones lock with cable mechanisms for opening by the: -

Electric in-car button. (Actuator for this on the door panel brace)

Door-mounted handle.

Door-mounted pop-up button.

Also, the lock itself has an actuator under a plastic cover that controls door locking, The door open confirmation microswitch is fed into this actuator.

Now from previous experience with these small DC microswitches, The contacts “fur-up” due to the low current load across them and the DC voltage.

So, the options to fix them in the past have been.

  • Replace it (preferred, not always available at 2:00 am when there are no parts, and the plant is down)
  • Get a big contactor with a juicy AC coil. Or a large DC one. And wire up the microswitch to the Contactor coil. Get it switching that contactor and the current will clean up those contacts for you.
  • Needing a way to defurr the contacts in the switch the other option is to operate the switch several hundred times by hand. Fairly roughly.


Not having options 1 or 2 available to me, I went with 3. You can remove the Microswitch from the lock by prising the material apart above the switch and lifting the Microswitch out. I then spent ages just activating the Microswitch. After a couple of hundred operations. I refitted the micro switch to the lock and rebuilt the lock into the door. After first cleaning out the lock of all debris with brake cleaner and regreasing it.

I was able to test the Microswitch operation by measuring the voltage across the pins in the actuator electrical connector. Please see Electrical Drawing below.

Currently, after many weeks the lock has been working fine. Long may it continue!

Please see the photos below. I'm hoping this will help someone as this door issue has been a constant source of frustration for me.

Door Closed Microswitch.

View attachment 141048





Microswitch next to its mounting point in the lock.

View attachment 141049





Door lock still connected to the Vehicle, Showing the cable connections and the Electrical Connections.

View attachment 141050



Photo showing the door closed micro switch cabling going inside the door lock actuator. This connector covers both the Door lock actuator and the Door closed Microswitch.

View attachment 141051



Below is the pinout for the Actuator and the Door closed micro switch.


Section M14/9 is the actuator and the micro switch. The section above it is the Sliding door contacts.

Looking at M14 the actual Door Microswitch is connected to pins 1 and 3. Pins 5 and 2 are connected to the Lock actuator, showing its current position.

View attachment 141052
Do the door contacts number from top to bottom? tx
 
Did you find a solution to this other than replacing the lock mechanism? I have the same problem intermittently and don’t really want to spend big bucks on the solution. Tx
The eu part went back. Ebay refunded the cost but, due to the masses of paperwork, I let the customs and VAT go. So no more eu stuff for me.

I have tried adjusting and improved the locking. I've sprayed with silicon lubricant and improved more. But if it persists I'll source a 2nd hand one. I then intend to see if a replacement micros switch can be engineered into the one I have.
 
It seems to me
The eu part went back. Ebay refunded the cost but, due to the masses of paperwork, I let the customs and VAT go. So no more eu stuff for me.

I have tried adjusting and improved the locking. I've sprayed with silicon lubricant and improved more. But if it persists I'll source a 2nd hand one. I then intend to see if a replacement micros switch can be engineered into the one I have.
that the simplest solution (other than fitting a new lock mechanism at £265) would be to fit an additional switch in the door pillar that the door contacts with on closure. It would need to be one that breaks the circuit when the door is open and makes the circuit when door is closed. It could just be wired to pads 2 & 5 and work in parallel to the lock micro switch. Is there anything wrong with this idea? I think many cars have this kind of arrangement rather than the more complex set up that Merc has gone for on the Viano.
 
So I tried the possible solution that m80 came up (but subsequently rejected as it was thought it would cause other issues) in order to see what the downside would be. I snipped the wires coming from pads 3 & 4 on the door pillar, then I connected together the stubs coming from the pads. Next I spliced together the wires coming from the door pins that contact the pads when the door closes ( just stripped the insulation a little without cutting the wires) I connected 2 to 3 and 4 to 5. This then gives a connection from 2 to 5 when the door is closed.
This fixed the issue with the rear central locking, pressing the key locks all the doors. I no longer get the ‘door open’ alert when driving either ; so two very annoying issues resolved!
Unfortunately the side effect of this ‘fix’ is that the door will not open when either the dashboard switch or the B pillar switch is pressed. Pressing the unlock button on the door or the outer door handle works fine. So the only downside really is that you can’t open the door from the drivers seat - something I never, or very rarely do anyway - so I’m very happy with this fix and definitely won’t be forking out £265 for a replacement door mechanism.
 
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An update on mine.

I use the o/s for doggy in / out, due to the style of the bench seat and being able to remove the single when it's facing rearward. So it has a higher usage count.

So it played up, sometimes it would allow locking, other times nope. It seemed that if I shoved it closed as it neared it's final point it could make a difference, but that wasn't reliable.

I had the lock out, tested the switches, and could see no issue.
I bought a 2nd hand lock anyway, but on earlier vans, but maybe just non electric, there is no child lock switch, or a 2nd lock sensing switch. Mine has an extra 4 pin socket on the lock.

I swapped the pads left to right, no difference.
This morning I swapped the pins, left to right, then tit failed to lock at any time.

So I connected up Star (well DAS, to compare doors. In fact now I didn't know which door might be causing the issue.
Thinking this was a temperamental connection inline some where, I had ignored the Star route, and even so when I was using it for other stuff the information from the door didn't show an obvious issue.

Anyways I could see no difference between the doors status wise.
But there is a normalisation programme, so I ran it.
Basically when the door is opened and closed it measures something. I don't see what it could measure in the lock, as there are only on / off switches, and mechanical open closed levers and such.
So I 'guess' it measures at the motor, this I haven't been into. But it must be where the signal for trapping a person must be generated at least.

Anyways, still early days, but it locked, and has done several times since.

I'll let you know if this is another red herring.

Btw, I did source a different type of micro switch, and designed how it could be held by 2 short self tappers.
That was on the 2nd hand lock, before I removed mine and tested to learn the micro switch is working as it should.
 
Well the previous remedy improved things,
but didn't cure the issue of the door sometimes failing to lock.

So today I removed and stripped the motor drive, and controller.
There was evidence of water ingress, that had caused some minor rusting on the motor, and minor furring on the controller pcb.
Best I can ascertain is that the rear opening window has allowed some water in.

The motor is simple enough.
2 wires to the motor, so poles must reverse to open / close.
2 wires to an electro magnet, that is part of the rotation counter.
4 wires to the sensor that sits around the segments of a plastic disc. So the segments rotating through the 2 sides of the sensor will be continually counted. Hence the normalizing.

My theory is that the water getting onto the plastic disc, might be corrupting the counts.
And it being sporadic means sometimes the count is good, sometimes not.

Does that sound feasible?
 
Hi all
I've been reading a lot about these side door issues and mine has been OK until 2 weeks ago and alas it's just as in this post it's all over the place LOCKSs .. dont LOCK etc. Now i'm a bit handy when it comes to electric as my background is in Telecommunications and fault finding and I think I may have found a cure but need to be 100% on where the pin lay out is as from the description and drawing posted from NotAT5 i want to be sure Im going the correct route as for around less than £10 I may have a fix for this and it wound take about 30 minutes to do but I want to test it all out first as mine is a UK England model 2009 Viano ambiente
( so passenger door is on the LEFT when SITTING in the van this could be detrimental when fixing it )
and just want to make sure the wire colour code is the same throughout the world if not then I NEED TO KNOW THE PINOUTS ON THE DOOR numbered top to bottom or bottom to top and ill get right on it and hopefully have a Fix for you all with out all the hassle of striping the van So NotAT5 please see attached and let me know the pin configurations Please ..

Regards Gary
 

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Hi all
I've been reading a lot about these side door issues and mine has been OK until 2 weeks ago and alas it's just as in this post it's all over the place LOCKSs .. dont LOCK etc. Now i'm a bit handy when it comes to electric as my background is in Telecommunications and fault finding and I think I may have found a cure but need to be 100% on where the pin lay out is as from the description and drawing posted from NotAT5 i want to be sure Im going the correct route as for around less than £10 I may have a fix for this and it wound take about 30 minutes to do but I want to test it all out first as mine is a UK England model 2009 Viano ambiente
( so passenger door is on the LEFT when SITTING in the van this could be detrimental when fixing it )
and just want to make sure the wire colour code is the same throughout the world if not then I NEED TO KNOW THE PINOUTS ON THE DOOR numbered top to bottom or bottom to top and ill get right on it and hopefully have a Fix for you all with out all the hassle of striping the van So NotAT5 please see attached and let me know the pin configurations Please ..

Regards Gary
Hi Gary, they number from top to bottom. I’ve rigged up a switch across 3 & 4 on the door pillar and connected 2 to 3 and 4 to 5 on the door. When the switch is made it puts a short across 2 and 5 as the microswitch would do upon door closure. So whenever I get the ‘door open’ message I just operate the switch. The message then disappears and the rear locking continues to work. It’s not perfect as I can no longer remotely open and close the door from the dashboard switch.
As I’m planning to do a camper conversion I’ll probably just go fully manual with the doors anyway. I’ve done a test of disconnecting all the wires and don’t really seem to have any issues. (Don't get the door open message and central locking still works).
 
OK so looking and reading on all this from the start is VERY CONFUSING !
So i've taken both NotAT5 and V6 Nut and broken it down & drew up a better schematic / Drawing to try and see where this fault is ...
I can see that the DOOR and PILLAR contacts that connect the micro switch in NatAT5 post seems to be the issue as per the micro switch issue not closing ....
It's possible that V6 Nut has other issues trying to understand why you have short out pins on the DOOR SIDE as well which lead to other switches by the look of it ?
But like most I press the Lock / Alarm button on the key fob and passenger and drivers door lock no problem but the side and rear dont and NO Flashing indicators .. I can see looking through the passenger side window on the dash the passenger door switch is flashing the led Indicating its not shut !
Now as i've hopefully worked it out correctly its PILLAR CONTACTS 2 & 5 (**SW1 ) connecting to 2 & 5 on the DOOR CONTACTS (**SW2 ) which in turn connects to pins 1 & 3 on the M14/9 ( this section is so confusing as well. Numbered badly with No 4 totally missing ? )
..
At some point now I have to Sort out some electronic relays & stuff and play but first I need to strip down the door pillar and door card and start taking some electrical readings .. I'm hoping that what i'm thinking and what it does are both on the same level for an easy fix .. right Multimeter and screwdrivers / Torx bits ...HERE I COME
 

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My efforts didn't resolve my issues.
I've taken to manually locking the rear 3 doors from within when parked somewhere more risky.
On keyfob locking, there is no indicator flashing, but all is locked.

Feel free to ignore this bit if it only confuses.
Gazza64, on your drawing I see the top 'M' as the lock mechanism solenoid.
The n/o micro switch as the lock micro switch.
The flip flop micro switch as the child lock micro switch.

The lower 'M' I see as the locking solenoid that is sited midway from the manual opening push actuator on the door, and the lock mechanism.
This split steel wire cable has an adjuster.
I've been meaning to remove my door card, yet again, to be sure that;
a) this steel cable line is seated correctly and,
b) to see if slackening the adjuster will allow for the system to see the door as reliably closed. I wonder if the micro switch in the lower part is being held open by a tight cable.

Having had locks out and bench tested, on mine, I couldn't repeat the unreliable micro switch theory within the lock mechanism.
Aside from confusing our testing, I think the child lock micro switch can be ignored. Although any frigs across those terminals might well confuse the SAM.
 
On the door side, I connected 2 to 3 and 4 to 5. This then puts a short across 2 and 5 when the door closes (3 & 4) shorted on pillar side) as per the microswitch. I don’t think 3 & 4 were used for anything previously.
 

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