Pneumatic door locks issue -- they all work perfectly... for about 2 seconds then...

solved: Pneumatic door locks issue -- doors automatically unlock after 3 seconds..

My 1996 B4V wagon is having an odd door lock issue.

Problem solved, explanation on post #27 of this thread.

From outside of the car, with all doors closed, using the key, EVERYTHING appears to work 100% correctly. Lock, unlock, windows open, etc. Likewise all doors, fuel door, tailgate all lock and unlock correctly using the key on the passenger's door. Yay!
However, from inside the car, with all doors open or closed, when I depress the drivers lock knob to lock the doors, all locks will correctly lock, but only for about 2 seconds, then they automatically unlock again. I invested several hours closely inspecting things, and I just can't seem to figure this one out! Door panels are off the front doors and rear tailgate, and I've experimented with systematically unplugging everything, and it continues to not work fine. It seems like an electrical switch issue, but I just can't seem to put my finger on it..
So this problem has been persistent since I bought the car this summer. I kinda decided to just live with it for a while, but last night someone broke I to my car and stole a bunch of important stuff... Because the doors were unlocked. So now I'm feeling highly motivated to finally sort this out.
I found this thread potentially helpful, but I still can't get on top of it.
https://forums.tdiclub.com/showthread.php?t=374634&highlight=Door+locks
Thanks for your thoughts!

how do the wires in the accordian look (between the door and the frame)?

Good idea, Mongler. I haven't looked, but will tomorrow.

I am suspecting that something that "says" the doors should be unlocked/unlicking is sticking. I'm not really sure how many bits can communicate that... I'm not sure if there's a central door lock controller. I guess both front doors have electric switches at their handle's key tumbler and at their vacuum actuators, plus the rear hatch has one at key switch? So 5 switches total that can give the input to lock or unlock?
*Shrugs*

I've tested with everything unplugged except the plug at the driver's door vacuum actuator. (So both plugs in the front passenger door, the driver's door handle's key switch, and the rear hatch were all disconnected at the same time.)

Then with all doors closed and engine running I locked doors by pressing down the driver's lock knob. All the doors and everything would still lock, then a few seconds later they'd automatically unlock again..

Would this indicate the electric switch in the driver's vacuum actuator is maybe sticking/malfunctioning? Or are there more pieces at play than I am currently aware of?

Mine does the same thing if the door latch freezes and the door won't stay shut. If I try and lock it from the inside to keep the door from flying open it only stays locked for 2 seconds and then automatically unlocks. Maybe some sensor is telling the lock system that the door isn't fully latched.

Jdulle, hmmm.

Does everyone else's car lock, then automatically unlock again a few seconds later when a door is open, if locked using the driver's door lock knob? Does it do this with all 5 doors, or just the driver's? This would be super helpful info... I was wondering if it were possibly some 'door ajar' safety feature..

the other problem i have come across is a leaking point at the motor or the vac lines in the doors.

Mongler98 said:

the other problem i have come across is a leaking point at the motor or the vac lines in the doors.

Click to expand...

Yes, but they seem to be operating quickly and correctly at all 6 locks. It seems to me that a leak would make them be slow, or hesitant, or something like that, don't you think?

Phi1osopher said:

Yes, but they seem to be operating quickly and correctly at all 6 locks. It seems to me that a leak would make them be slow, or hesitant, or something like that, don't you think?

Click to expand...

try pulling off the connection at the pump and putting your finger on it to seal it, if the motor sounds exactly the same in pitch, then it's not a leak or issue with the motor, a leak will make it sound much faster or high pitch without the draw low lowering tone.

Thanks Mongler. I'm pretty certain the pump is working perfectly..

I am continuing to struggle with these lock... Arrrggg

Well I dont know. Maybe it's a wireing issue. I dont have much experiance with this part of the car. I am parting out my mk3 Jetta so if you find you need a replacement part for the locking system or anything, pm me.

Quick question: do you hear the compressor before or after the driver's side lock knob goes back up? Just a fraction of a second, but what comes first?

Ralphy said:

Quick question: do you hear the compressor before or after the driver's side lock knob goes back up? Just a fraction of a second, but what comes first?

Click to expand...

I'm not sure. the compressor motor is so quiet, I never hear it from the front of the car. I'll have to get one of Daddy's little helpers to help me!

Phi1osopher said:

I'm not sure. the compressor motor is so quiet, I never hear it from the front of the car. I'll have to get one of Daddy's little helpers to help me!

Click to expand...

WHAT? that vacuum pump (not a compressor) is crazy loud, at least mine is, its loud enough to hear it over a diesel engine at least.

Mongler98 said:

WHAT? that vacuum pump (not a compressor) is crazy loud, at least mine is, its loud enough to hear it over a diesel engine at least.

Click to expand...

Yeah! Even with the motor turned off, I can't hear the pneumatic lock's electric motor/pump in the back of the car. I can lock and unlock the doors all day long and they do it silently.

Mongler, are you saying yours makes a sound? That seems odd to me!

yes, a LOT of sound, a nice low and slow numatic sound that goes down in pitch as it gains vacuum.

So when the doors all automatically unlock again, where is the
Key? Is it in the ignition switch or not? I’d try it again twice just to see how it acts.

I’d also test the drivers door handle micro switch for proper function. Just a hunch.
I’ve never known the electric vac pump to make noise....it should be inside a
formed styrofoam clam shell enclosure.

I can definitely hear the pump when the car is not running, as I’m walking up to it, using the fob. It’s this way on both of my B4s and the Rotbox.

I don’t recall ever locking the doors when I’ve been in the car. I decided to test this and I definitely was able to hear the pump, while the engine was running. It’s not crazy loud, but it’s definitely audible.

All pumps are in their styrofoam clamshells.

-Todd

Let me get this correct now, you're trying to lock the driver door with the driver door open?

If that's the case it won't do it, you're not supposed to be able to lock the driver door if it's open or not fully latched. That's to prevent you from locking your key in the car.

If that's not the case it sounds like you have a problem with the latch in the drivers door.

My lock pump makes noise, it's not very loud or very long, just enough to cycle the locks and then it shuts off.

Steve

ToddA1 said:

I can definitely hear the pump when the car is not running, as I’m walking up to it, using the fob.

Click to expand...

Steve Addy said:

My lock pump makes noise, it's not very loud or very long, just enough to cycle the locks and then it shuts off.

Click to expand...

That's right...I remember now. It's a labored growling noise. Mine has been too long off the road

Thanks for the feedback!
First, I can hear my pump, but it is pretty quiet. It seems to be operating 100% correctly.

Here's my problem: When I am sitting in the car, with the doors closed and the windows closed, when I lock the doors using the knob at either of the front doors, all the doors will correctly lock, but about 2 seconds later they will all unlock again. Again, this is only with the door lock knob when locking the doors while sitting in the car. This will happen with the key in the ignition or out of it, with the engine turned on or off, with the car parked or driving down the highway.
When I manually lock from the inside the car all the doors lock, pause, then unlock themselves. All 6 actuators: four doors, the fuel hatch, and the rear lift gate all working correctly, quickly, and apparently effortlessly, every time... except then they unlock themselves.

However, when I am outside of the car, with all the doors closed, and I use the key to lock the doors, then they all 6 actuators will lock correctly and stay locked.

Phi1osopher said:

Thanks for the feedback!
First, I can hear my pump, but it is pretty quiet. It seems to be operating 100% correctly.

Here's my problem: When I am sitting in the car, with the doors closed and the windows closed, when I lock the doors using the knob at either of the front doors, all the doors will correctly lock, but about 2 seconds later they will all unlock again. Again, this is only with the door lock knob when locking the doors while sitting in the car. This will happen with the key in the ignition or out of it, with the engine turned on or off, with the car parked or driving down the highway.
When I manually lock from the inside the car all the doors lock, pause, then unlock themselves. All 6 actuators: four doors, the fuel hatch, and the rear lift gate all working correctly, quickly, and apparently effortlessly, every time... except then they unlock themselves.

However, when I am outside of the car, with all the doors closed, and I use the key to lock the doors, then they all 6 actuators will lock correctly and stay locked.

Click to expand...

That answers my question, about having the door closed or not, which was not mentioned before so it wasn't clear.

I think your problem is in the door latch mechanism or more specifically the connection with the lock pin / rod inside the car.

Since the key and the lock pin are different connections with the latch mechanism (and the micro switch) and the handle lock is working properly, that tells me that the alternate connection, the inside lock rod, is obstructed in some way at the latch or maybe bent. I can't blame this on the micro switch, it's working fine with the handle so it should work fine with the inside as well.

The behavior you describe is typical when the pin lock didn't stay down far enough, it initially locks because the switch inside the latch was triggered but it reverts a few seconds later because it the rod didn't stay in the correct position, for what ever reason.

Try unscrewing the pin lock knob about six or eight turns and then attempt to lock the car again. If it exhibits the same behavior as before then check the lock rod attachment at the latch to see if there's some obstruction or maybe the lock rod is bent a little?

I would also shoot some white lithium in the latch mechanism to see if that frees up anything.

Steve

Steve Addy said:

That answers my question, about having the door closed or not, which was not mentioned before so it wasn't clear.
I think your problem is in the door latch mechanism or more specifically the connection with the lock pin / rod inside the car.
Since the key and the lock pin are different connections with the latch mechanism (and the micro switch) and the handle lock is working properly, that tells me that the alternate connection, the inside lock rod, is obstructed in some way at the latch or maybe bent. I can't blame this on the micro switch, it's working fine with the handle so it should work fine with the inside as well.
The behavior you describe is typical when the pin lock didn't stay down far enough, it initially locks because the switch inside the latch was triggered but it reverts a few seconds later because it the rod didn't stay in the correct position, for what ever reason.
Try unscrewing the pin lock knob about six or eight turns and then attempt to lock the car again. If it exhibits the same behavior as before then check the lock rod attachment at the latch to see if there's some obstruction or maybe the lock rod is bent a little?
I would also shoot some white lithium in the latch mechanism to see if that frees up anything.
Steve

Click to expand...

Thank you Steve!
If it helps, I forgot to mention that as I was trouble shooting this problem, I observed the same "lock and then automatically unlock" behavior with EVERYTHING unplugged. This includes everything from the front passenger door was unplugged, the rear lift gate's switch was unplugged, and the driver's door's key's micro switch was unplugged -- so I believe only the 6-pin plug for actuator in the driver's front door was still plugged in. (Unless there are also switches in the rear doors that indicate if they are open or closed? I didn't get to those yet).
In addition to this the dome light is working correctly and seems to be timed correctly, illuminating when I open doors, and turning off correctly when I close them. This seems to indicate that the "door open" switches are currently working correctly, helping to further isolate that it probably is something not switching correctly inside the front driver's door's pneumatic actuator.

Actually, my original thoughts aren't correct.

I forgot that on these cars there are two micro switches that actuate the central locking system, one inside the door handle and one inside the latch itself. Either one can trigger the system to lock or unlock. As a curious test try operating the locks from inside via the passenger door with all them doors closed. I bet it will work fine from that side.

You should still check to see whether there's a problem with the inside lock rod as a first response but it's no longer a case where there are two triggers for the same switch, there are two switches in this system per door.

If there's no obstruction at the latch for the lock rod inside the door I'm betting there's a problem with the latch micro switch and I would say you need to pull the latch and replace it, or at least pull the latch and clean it out maybe. You can probably check / test the connection with it still in the door although I've never done that. I also don't know how the switch is mounted in the latch although the parts catalog shows it as a separate entity. I can't say I've ever dismantled one to replace this part though. I suppose it could also be faulty wiring for that latch micro switch, before pulling the latch I would check the wiring to that switch to verify it's not broken or shorting through the accordion hose.

My Mk3 has a failed door latch micro switch that triggers the alarm when I use the key to unlock, so I just use the fob instead and avoid it.

As for the pump mine makes more of a moaning sound for maybe three seconds.

Good luck and report back with anything new.

Steve

Phi1osopher said:

last night someone broke I to my car and stole a bunch of important stuff... Because the doors were unlocked.

Click to expand...

When I manually lock from the inside the car all the doors lock, pause, then unlock themselves.

. . .

However, when I am outside of the car, with all the doors closed, and I use the key to lock the doors, then they all 6 actuators will lock correctly and stay locked.

Click to expand...

So when your car got burglarized, you didn't lock the doors from the outside?

turbodieseldyke said:

So when your car got burglarized, you didn't lock the doors from the outside?

Click to expand...

As sad as it is, that is correct. I was working a long 72 hour shift with EMS, and I was simply stupid-exhausted. I made a quick food run, and when I parked I got distracted and left the doors unlocked. That's all on me.

To live in the one state where you're allowed to defend your car with extreme prejudice.... but be in a sleep-coma when the burglar hits? That's bad luck right there.

Sounds like the solution is to either use the key, and/or install a keyless remote (aftermarket, or Mk3). I always thought the B4 should have a door lock/unlock button like the Mk3.

door locking problem solved: cabin locks will lock correctly, then automaticallunlock

YAY!! It's update time with good news. Yesterday I was able to invest about 5 hours with a multimeter and a few volt testers and finally chased down the problem with my door locks. I have spent the past few weeks driving around with the door and rear hatch panels removed, and the interior of my car felt like a chaotic mess. YUCK! I can't say how good it feels to have it all back together again and feeling the lovely Passat it was meant to be!!

Here's the short version: I had an elusive door locking problem: the cabin door locks would lock correctly, but would automatically auto-unlock after about 3 seconds. All other door locking features worked correctly.
My problem was that lock knob's threaded rod needed to be adjusted where it connects to the Vacuum-Lock Actuator. I also think the slide in my vacuum actuator might have had a small sticking part in it.

After hours re-familiarizing myself with the circuits, carefully, meticulously going through it all, one bloody wire and vacuum hose at a time, plugging and unplugging everything repeatedly, removing the door-hinge-boots to visually inspect the wires, and all that fun circuit-chasing stuff, I finally got the "wiring problem" narrowed down to being 95% likely that it was some internal short circuit inside the front driver's vacuum locking actuator. I was worried this would be a $200 part, but looked and found a cheap used one on evilBay for about $20 shipped, so I went ahead and ordered it. The VW part number is 3A0 862 154A, and I believe the same assembly will work on either the left or right. Here is the one I bought; I am only sharing the link because I think the additional photos probably are helpful while they last..

Then, freshly emboldened with the confidence of a replacement part on it's way, I went ahead and disassembled my vacuum actuator. It wasn't designed to be user serviced.... I discovered that there is a simple micro switch in there (I'm pointing to it in the 1st pic, and it's blue) which is pressed when the door is locked, and released when the door is unlocked. For the front doors and tailgate, when the ignition is on and the doors are all closed, their respective switches constantly send a signal (+12v) from the actuators to the locks' air pump. (The pump has a surprising large number of wires attached to it!) The pump then will fully pressurize or depressurize the bi-directional pneumatic line, running until an internal pressure switch inside the pump assembly is triggered, disengaging the pump. Once the locks are fully articulated and the pump has turned off, the lines do not need to be pressurized (or depressurized) for the locks to stay in their position -- they will only automatically change while the pump is working. If one line is removed or damaged and the locking mechanism is activated, the pump may run forever ...or until the battery dies, whichever happens first... For the driver's door there is a 3-wire connector with constant (+) 'power in' and two 'return wires' that alternate a return (+) signal back to the pump depending on whether the door lock's knob is in the raised or lowered position.

For me, it turns out that the threaded lock knob that attaches to the actuator needed to be adjusted to be longer. (The lock knob rod is in two parts, a 1st part that goes from the knob to the door latch/lock mechanism, then a 2nd part from the latch/lock to the actuator.) When I manually pressed down my lock knob it was just barely long enough for the actuator to make contact to with its internal micro switch -- I would press the door lock knob and it would move down, make contact with the micro switch, and activate the pneumatic locks, but when I released my manual pressure from the lock knob it would slightly rebound and because it was too short, it was no longer pressing the internal micro switch. So my doors would lock, then about 3 seconds later they would automatically unlock -- because the micro switch was pressed, then released. Adjusting the rod to be slightly longer corrected this so that when I manually pressed the door lock knob it would now travel a few millimeters farther down, making full contact. (There also is a small black lever inside the actuator (not shown in the photos) that toggles between the slide and micro switch. I suspect that this lever may also have been stuck.. )

The above description can possibly be imagined from considering my first photo of the disassembled bidirectional door lock vacuum actuator. (that's just fun to say: 'bidirectional door lock vacuum actuator.') On the left is the wiring component with the blue micro switch. At the top is the sliding portion of the assembly. Unseen is the internal vacuum diaphragm at the bottom of the actuator. The slide attaches to the 'lock knob rod' at the black part at its top, and it the slide's bottom 'snaps' on to a vacuum diaphragm inside the actuator via a small black nipple (also not shown in the photo). On the left side of the slide there is a 'high' and 'low' depression where, as it moves up and down, it interacts with the micro switch. Sadly this is not easily seen in this photo, but it accounts for the signal triggering as the door is locked or locked -- either manually by the lock knob or automatically by vacuum actuation.
The actuator assembly's little plastic tabs were all pretty fragile and one snapped when it was disassembled, but it all securely snapped back together and it all works correctly now. I did not have to get into the sealed diaphragm part of the actuator.


My disassembled actuator.



The driver's front lock actuator



If you look closely you can see that I "unscrewed' the actuator about 5 or 6 threads. I need the rod to be a bit longer.




I hope all this will possibly help future users better understand this component.