Microswitch for latch

[26DIPP]

The central locking is playing up, locking and unlocking whenever it pleases. When you lock the car, it sometimes works, the dash also does not always show the door open.

So I guess it is one of the microswitches. Skoda will sell me a complete lock / latch for £130, but no separate microswitch.

skoda-parts.com do a microswitch and postage is 3x more than the switch. Are there any places in England that will do the microswitches?

[UrbanPanzer]

https://shop.bmacvags.com/products/vw-audi-door-module-microswitch?variant=5883674947

[Breezy_Pete]

If you do replace microswitch plus wiring all the way back to the solder joints, check the connector pins for play while you're there.  May be hard to see cracked joints, as the whole board is covered in some sort of varnish, but wiggling the connector relative to the board may cause something to catch your eye.

Here's one with varnish scraped away from the incoming earth pin:

 

 

[KeithCheetham]

 Wino may be the best person to answer this with his understanding of wiring diagrams, but what is the the operational function of this switch - does it send a single signal when locking/unlocking or does it latch in a open or closed position, the action of the lock on the switch may also identify this. Regarding the OP issue, has it been confirmed that there are no broken wires in the the "elephant trunk" between the A post and door, and is the issue just when securing or opening the car, or when driving.

[chimaera]

1 hour ago, KeithCheetham said:

 Wino may be the best person to answer this with his understanding of wiring diagrams, but what is the the operational function of this switch - does it send a single signal when locking/unlocking or does it latch in a open or closed position, the action of the lock on the switch may also identify this. Regarding the OP issue, has it been confirmed that there are no broken wires in the the "elephant trunk" between the A post and door, and is the issue just when securing or opening the car, or when driving.

There are actually a few switches inside the lock module, reporting the state of the different moving parts. One is for door open/shut, a second for locked/unlocked, and a third for whether deadlocking is active. I have pictures somewhere of one of these disassembled which shows the different switches. I'll dig them out later and add them here.

 

 

In my experience it has been the solder joints that have failed rather than the switches. It's easy to check with a continuity tester.

Edited 23 May, 2021 by chimaera

[Breezy_Pete]

1 hour ago, KeithCheetham said:

 Wino may be the best person to answer this with his understanding of wiring diagrams, but what is the the operational function of this switch - does it send a single signal when locking/unlocking or does it latch in a open or closed position, the action of the lock on the switch may also identify this. Regarding the OP issue, has it been confirmed that there are no broken wires in the the "elephant trunk" between the A post and door, and is the issue just when securing or opening the car, or when driving.

The door open switch (on the outside, rather than one of the PCB mounted ones) just shorts pin 8 of the connector to pin 7 (earth), whenever the door is open.

 

[26DIPP]

I "opened" the door to check access and if, what part I would need. I took the latch / lock out and while handling it, the CL did its trick again. After taking some pictures, I unclipped the outer microswitch, cleaned it, refitted it and put the door back together. Strange enough, the CL is not clicking anymore at will. I think it may just be a matter of time before the unprovoked actions are back. For now I will leave it. I did look at the youtube video about the opening of the electric part of the lock and will have a closer look at the circuit board then.

 

Looking at the current flow diagram for the doors, the likely problems are the microswitches and the solder points to earth and pins 8 and 4.

[26DIPP]

The door lock played up again, so it was time for a more serious look.

 

I opened up the door to get the lock out.

The next step was to examine the lock. To open it you separate the mechanical part from the electrical.

 

In the electrical I took 1x T15 torx and several T10 Torx out and you can open it up.

I reconnected the lock and played with the microswitches to figure out which one was playing up.

 

The one circled seems to register the open and close states and this one was faulty. I am not sure what the other does because it does not make an obvious contact. As I had ordered the door contact one on the outside but none of these I decided to just desolder both and swap them. On the other side of the circuit board you can see that both switches have 3 pins and while switch 1 uses pins 1 and 2 the other uses 1 and 3. Both switches use different pins and I hope that by swapping them the so far unused contacts inside will work. Resoldered and I connected just the circuit board and it functions as it should.

Fitting is just the reverse of opening the door.

[Breezy_Pete]

Well done for getting it going again.  

 

According to the WDs those two microswitches feed back 'locked' and 'deadlocked' status if I'm interpreting this correctly.  (The pin 5 connections below).

Looks like the resistor tracks to the one you found trouble with, so that must be the deadlocked/Safe one.

 

The two microswitches not fitted on that lock of yours are the ones that go to pin 4, registering the key position on locks with keyholes. Key neutral/upright results in that pin being open circuit, then the two (locking / unlocking) positions result in the two states shown there.

 

"No resistance" where mentioned below means "short to ground/earth".

Edited 14 June, 2021 by Wino