I have had problems with two of the doorlocks on my Mexican-built, 2007 A5 TDI Jetta.

The problem first arose exclusively with the driver's door, whch suddenly refused to unlock when the relevant button on the remote-control fob was pressed. The only way of unlocking the door was by turning the key in the lock. After a few weeks, this problem mysteriously resolved itself and the lock has since functioned perfectly.

But later the right-hand rear passenger door also began to refuse to unlock in response either to the remote or to the central locking button on the driver's door, and of course, unlike the driver's door, the passenger doors have no key slot as an alternative means of opening them. Normally, when the unlock button on the remote is pressed, each door-lock makes a 'kerlunk' noise as it unlocks. Instead, the problem lock emitted a 'click-click, click-click' sound. This implied that the appropriate signal was reaching the lock via the bus but that the lock was not responding correctly. The fault was intermittent and occasionally the lock would deign to release, but it was usually necessary to alternately push the lock and unlock buttons on the remote numerous times to achieve this. The intermittent nature of the problem suggested the possibility of a poor electrical connection, and it seems this was indeed the case.

The dealership's service department diagnosed a defective lock-module. They were clearly familiar with the issue and had evidently dealt with it on a number of occasions. While they said only a small percentage of the VWs they had sold had been affected, it nevertheless suggests to me that the problem may be fairly common. If so, and given that the inability to exit through a door quickly in an emergency could be seen as a safety issue, I'm surprised there hasn't been a recall.

I was hoping that if the cause were indeed a poor electrical connection, it might be possible to simply make this good, rather than replace the entire lock. But evidently the locks are regarded as non-repairable and are simply replaced in their entirety if faulty in any way.

Working on the lock module entails taking off the outer panel of the door. But the screws that secure this panel can be accessed for removal only with the door open. So it's fortunate that the lock, albeit with difficulty, could be persuaded to release.

With the aid of the Bentley manual, I could have replaced the lock myself, but I would have had to purchase (or make the equivalent of) a VW special service tool (T10118). But in the end I decided to let someone more familiar with the task, namely the dealership service technicians, do the job, an exercise that cost me $465!

Perhaps it isn't economically feasible for a dealership service centre to attempt to repair rather than replace a lock. However, having obtained the faulty unit for examination, I cannot agree that they are necessarily completely non-repairable. I was able to non-destructively separate the electronic module from the rest of the lock and open its housing to access the internal components. The image file Jettalock01 shows the opened electronic module with its printed-circuit board (PCB) and associated components, still in one of the two halves of the housing. Jettalock02 and Jettalock03 show the two sides of the PCB after it was lifted out of the housing.

The electronic module contains two servomotors, which are labeled A and B in the photos. I was surprised to find that instead of using soldered connections at these motors, VW had used metal-strip conductors, the ends of which simply plug into sockets on the motors and have no latching arrangement to secure them. With the larger of the two motors, B, the conductors seemed to be reasonably firmly gripped in their sockets, but in the case of A the connection was so loose and insecure that gentle shaking of the PCB was enough to cause the motor to fall off.

I am satisfied that the poor connection at motor A was the cause of the intermittent fault exhibited by the lock when it was in the car. No other fault appeared to be present on the PCB or the components mounted on or attached to it. I assume this method of connecting the motors is faster and cheaper, thereby saving what can hardly be more than a few cents on the production line. But as I now know to my cost, this can translate to considerable inconvenience and a penalty of some hundreds of dollars for the unfortunate owner of the vehicle.

In one of the two halves of the housing of the electronic module, a short length of foam adhesive-tape had been placed such that when the housing was closed this tape pressed down on the part of motor A where the two connector strips enter their sockets. This had evidently been done to help keep the connectors in place. No such provision had been made for motor B, where, as noted above, the conductors were more firmly gripped by their sockets. My suspicion is that the insecure nature of the connection to the smaller motor was already a known issue during assembly of these locks and that the foam tape was an attempt to dodge around the problem without the expense of re-engineering the method of connection.

My apologies for the mediocre quality of the pictures, which were shot with a mobile phone.

Edited by: althepom on Jul 15, 2011 1:47 AM

Thank you for the great follow-up!

I have not yet run into this myself, but will keep your post in mind!

Although it's the other three doors that won't alway lock, my guess from your description is that the problem most likely is with the lock on the driver's door. A VW service agency that has dealt with the exact same problem before might be able to give a more confident opinion.

The procedure for accessing and removing the front door lock is detailed in pages 57-3 to 57-6 of the Bentley service manual for the 2005-2010 A5 Jetta and I would very strongly recommend perusing that information before you decide whether to attempt the task. It entails first prising the plastic cover strip off the rear edge of the door. This gives access to a hole in the rear edge of the door and through which a torx screwdriver can be inserted to slacken off the screw which holds in place the lock cylinder (the part into which the key is inserted) and the associated external door handle. Having then removed the door handle and lock cylinder and detached the release cable from the door handle, it's necessary to take off the external door panel, which is held on by a retaining screw under the door handle and (in the case of the front door) 18 bolts of three different lengths along it's front, lower and rear edges. The lock module is then accessible. The wiring harness connection to the lock module has to be unplugged and the other end of the release cable has to be unhooked from an actuating lever on the module. The module can then be removed by unscrewing the two bolts that secure it to the rear edge of the door. Reinstallation is the reverse of this procedure but involves the use of a special VW sevice tool to correctly position the end of one of the springs in the actuating lever of the lock mechanism.

Having extracted the lock module, it's possible to remove several cross-head screws etc to separate the electronic part from the mechanical part and to open the housing of the electronic part in order to inspect the contents. In my case, I had the entire rear-door lock module replaced at the service agency and merely examined the faulty original to determine why it had failed. I didn't actually repair it.

Although the problem you're experiencing, like mine did, shows intermittent symptoms suggestive of a loose electrical connection, I wouldn't assume the exact cause is identical, i.e. involving the connections at one of the servomotors. I've read of similar lock problems caused by dry soldered joints and faulty microswitches. (There are two microswitches directly mounted on the printed-circuit board of the lock module. A third, attached to the PCB by fly leads, senses whether the door is properly closed.) As well, at least on earlier models of the car, some lock failures were attributable to fracture of the wiring where it enters the door, and so gets repeatedly flexed.

I'm puzzled why you're getting such a short life from the battery in your key fob remote control. I've only been using one of the two keys that came with my Jetta and that key has been going now for nearly four and a half years on its original battery.

Best of luck in attempting to resolve the problem!

My back passenger door lock has stopped locking/unlocking on my 2006 Jetta. This is a concern to me with kids in the back seat. I believe that this is safety problem and that a recall should be pushed for.

This is an update to my original post at the head of this thread.

A third lock on my 2007 Jetta has now started to intermittently refuse to open - this time it's the one on the front passenger door. I'm hoping it may cure itself, like the lock on the driver's door eventually and mysteriously did. I'm not anxious to fork out another $465 to have a VW dealership replace the item, particularly when, in my opinion, the issue should have been resolved via a recall at no cost to vehicle owners. Three out of four failing at different times on the one car must be more than random chance and reinforces the evidence of a design and/or construction fault with these locks.

I wonder if exactly the same lock module is still being used in current models of the vehicle?