deezell

Had this common fault on two doors almost simultaneously, front left intermittent, rear left permanent. Annoying to have to go to the right hand side to unlock the left doors from inside. The front had been replaced in 2013 with one from the breakers off an A3, I suppose I got got nearly two years out of it. Looking at maybe 400€ for a pair of new ones, I decided to investigate the inside of the locks when removed. There is a little grey cover held by one screw which exposes the lock mechanism, two positional relays and the cams which actuate them on lock/unlock. I noticed the the upper cam was not rotating on unlock, leaving the lock engaged and the relay closed. It would rotate though with a little assistance. I doused the mechanism in spirit to flush out any stiff muck, then again with Wd 40. After a number of cycles the cam began rotating on unlock. I tested it for ages, it stuck once, but I recalled something elsewhere about low voltage, so I started the car and gave it a charge. After this it just kept working. The intermittent front one got the same treatment, both now working fine, fingers crossed. Heres a little youtube of the old one I removed in 2013, showing the fault


*****

royclark

You don't say what model you have, A6 C5/C6 and year?

deezell

2007 A6 C6, the door locks are common to the A3 and A8 also, check partsbase.org for years and models. Since this post, the rear one has failed again, the front was intermittent a couple of times. This is a 250 euro part, and one from the breakers may already be on its way to failure, so I decided to take a closer look at the original failed one I removed in 2013. I wasn't convinced it could not be fixed, and i was right. I managed to seperate the mechanical lock from the grey electrical actuator, opened this up, and as I suspected, the motors are push fit into the internal frame, with tiny spade connectors on this which insert into the motor. Sure enough, one of these was black and pitted, ensuring a poor or open connection to the motor. A careful abrading of the pin and the motor contact, reassembly, and the actuator worked. Buoyed by this I removed my faulty rear door actuator, the fault was exactly the same. Rear door is now fine, and I have a fully functioning front door one to replace if my current front actuator expires, though it will be just as repairable. It is tricky to separate the actuator unit from the lock, so I'm going to post a few pictures to help others achieve this really cost effective repair, as a dealer replacement could run to 400-500 bucks. Watch this space.

deezell

To dismantle the lock, undo the three screws that hold the white/grey actuator plastic case to the mechanical lock part. These screws may be marked with blue loctite. when these are out you can start pulling the two halves apart slowly. The first picture shows the actuator as it seperates from the lock mechanism. The two rotating cam shafts which actuate the relays are also connected by spring loaded cranks to two plactic slide latches in the lock, one yellow and one green. The right side yellow one will seperate easily under the force of the gentle pull, but the left sidegreen one will not, and will probably pull the spring mounted crank off the end of the cam. This and it's spring is easily replaced after it has been prised carefully out of the green slide, it pushes back onto the end of the shaft and engages with the shaft with about 180' of spring loaded rotational play.
The second pic shows the yellow and green latches, the yellow one is the one which engages the outer door lever with the door lock. when thsi yellow slide is pulled down by the right hand crank, the outer door lever no longer connects to the mechanism.
Third picture shows the cranks which are mounted on the ends of the relay cams by springs which give them an amount of rotational back play. I've replaced the green slide crank which pulled off during the seperation. To remove this crank from the green slide requires a needle nose pliers and a flat blade screwdriver to compress the long spigot and draw it out of the green slide, careful not to break it.
The long black lever over the green and yellow sliders is there to engage with the right cam when it is upright (locked) so that pulling the inside door handle will rotate the shaft back to the open position and re-engage the outer handle via the yellow slider.
Picture 4. There are 7 screws on the actuator case, the case can then be split with the help of a putty knife or thin scraper blade. Take care to preserve the rubber seal between the two halves. Note you can't split this case prior to dividing the lock, as one of these screws is concealed by the lock mechanism half. That would be too easy
Next picture shows the motors and gears, the indent spring may pop out , place it back as in the picture before reassembly. The big motor is the one that gives the problem, it just pulls up and out

deezell

With the motor out, you can clearly see the burnt residue on the left hand pin. Clean both with fine sand paper or a miniature file. I used a folded piece or fine wet and dry to insert into the motor receptacles. If you want to test, the rearmost pins on the multi connector directly connect to this motor's pins. Replace the motor, screw on the cover, insert this part back into the lock part, lining up the spigots on the ends of the shafts with the green/yellow slide holes. The long spigot will push into the green slide with the pressure of pushing the halves together, but you will have to reach in under the yellow slide with a small flat blade screwdriver to click it back onto the right hand shaft, as it will otherwise just push ahead of the spigot. Replace the three screws that join the two halves, leave the cover off until you have plugged in the door cable and tested the lock/unlock function. If all is well, put on the cover, and put the lock back into the door and smile. There are instructions elsewhere for removing the locks from the A6 C6, if I can find the link I'll post it.

royclark

Thank you for this VERY useful post.
How long did it take you to remove the lock from the door ?

deezell

Probably hours the first time, but I have it down to 15 minutes now. Five door card screws, two under the trim behind the inner door handle (prise up and slide back), one under the tweeter grille ( front door) or upper speaker grille ( rear door), prise out carefully, one in a long recess under the door handle, (really long philips driver and X ray vision) and one at the base of the card. Card pulls out with a hard tug from the bottom, hinges up and lifts off from next to the glass. Undo speaker plug, window switch plug (a lever release on the front, a red pull out tab on the rear). Unhook the the door opening cable. Stow the card. Peel back the plastic seal from the lock area, about three quarters way down. Front door, remove the bass box speaker from the door. If you can, reach in and uncouple the power lead from the bottom of the lock. Unclip the rod from the outer door handle by rotating the plastic retainer clip inwards and pulling out the rod. Undo the two star head bolts from the lock. With your hand inside the door frame, hold the lock and feed the bowden cable back into the frame. For the rear door, the lock should then rotate around the inside of the window carrier frame and from there out through the door frame. The front is trickier but it is possible to remove without unbolting the window frame. When the lock is loose, Unclip the bowden cable from the mechanism, you'll need to maneuver it into a suitable position. It's also advisable to remove the outer handle rod from the mechanism by flipping up the black/ yellow clip on the lever. To get it past the window frame, I found that turning it upside down first, then rotating it around the outside of the window frame works. It's tight, but it just squeezes by once the bowden cable is removed.

I've no pics but I'll post a couple of the card screw locations. Final thing, on reassembly, check that the door card clips came away with the card and are not still stuck in the door frame. These can get stuck solid over time, so if they are still stuck in the frame, prise loose and slide them back into the door card. Some may have broken, cheap to buy, or get from a breakers. If they were stuck it will take a very firm pull to either release them or pull them off the door card slots. Reassembly is the reverse, getting the outer door handle connecting rod back in is hard if you have hands like clubs. ( me), get a kid or girl to help here. If you've removed it from the lock end for the front door procedure , then attach it to the outer door handle first before re inserting the lock, then clamp the straight end in the black yellow clip when the lock is bolted in. If you try doing it lock side first, chances are you will not leave the rod the correct length to exactly mate with the upper outer door handle lever. The black/yellow clip is an adjustable clip which grips the road's serrated end. This clip when fully open can be clicked into position on the lock mechanism to stop it rotating and falling off while maneuvering the lock past the frame. It's a one finger operation to pop it loose and grip the rod. One other thing, The drivers door has an extra connecting rod to account for the manual key unlock. I've not done this door yet, but I read of people breaking this because they didn't figure out how to uncouple it. Its covered in some other posts elsewhere.

royclark

What a great write up.
Thanks for taking the time to do it.
My passenger lock has intermittent fault (2009 A6 Avant), I will have to get around to doing it sooner or later.
Trouble is, if I have a go at this and **** it up I will be left without the car until I can get a new lock.

deezell

It helped that I had the old faulty lock to work on. You can buy used locks on ebay, or from a breakers. They might work for years or show this fault eventually, but for 50 quid it's worth a chance, and you have to old lock to play with. Front and back passenger locks are almost identical, just the child proof cam in the back one, but they can be interchanged in a fix.

haloguy628

Common problem on VAG cars up to I believe 2003? That's when VAG reengineered the microswitches in the latch. Real PITA to change as you have to take apart the whole door interior to get to it.

Edit. The problem I described was on the B5 Passat and B5 A4. Those latches were reengineered. Seems like our cars have the same problem.