Take the door panel(s) off and look at the linkage...common problem that a piece "drops off".
Also check the wiring in the door bellows...another common problem....loads of posts about it if you search.

 

Thanks Gaz, I'll have a search (sorry, should have done that first). I'm not very technical but I'll give it a try.

 

Sounds like the actuator has seized Up.

 

If the actuator had seized, it wouldn't keep "cycling" the lock!

Nothing wrong with basic system.....but does anyone ever think to clean/lubricate the mechanism (until it fails) ???

BTW, your tailgate and slider will also be doing the same thing....just less noticeable.

 

dispensing with problematic central locking is not such a bad idea, especially when it’s VAG central locking 😂

 

Sorry, don't know about the winders....mine are electric windows.
To remove the panel, unclip the pull handle cover and remove the screws inside.
Then there's one more screw at the front on the pillar/frame.
Unscrew the lock burron.
After that LIFT the panel upwards (many people damage them, assuming the panel pulls away on clips).

Chances are the actuator has a piece that has become loose, and catching on the mechanism.
Not being able to manually unlock it suggests it's NOT the actuator motor.
The latch is a 2 stage device, if the 2nd stage is catching, you may have to use a bent coat hanger to try open it.

Either that, or park in a "dodgy car-park", and wait for some little tea-leaf to come and break in!
If you have break down cover, it will take them 2 mins to get it open.

 

Brilliant. I'll attempt tomorrow. Thank you for the advice and instruction. Get ready for lots of crying emojis when I've completely f'd it up!

 

Seeing as your drivers door is "stuck", may be an idea to tackle the passenger door 1st.
That way, you'll get an idea of what-goes-on inside the panel and lock mechanism.

 

You can check the actuator with any battery, 9V will be good enough. Just take a 2 piece of wire, connect to the battery and actuator. If it moves - then it works. But try different polarities, because when it's locked, it's not gonna move again, only other way (change + & -).
Also, it can be a problem with wires (very common). You can check it with a multimeter. Central lock sending signals to different wires. But I don't remember colors, should have a video somewhere.
The lock unlocks after locking because it doesn't see any signal from another door (it should be locked).
If you had it before, and then it became even worse, then it is highly likely the wires.
Also, you can check the harness for any bad wires with a multimeter. You just have to test it for continuity by testing both sides of the connectors (just be careful when testing pins on the male connector (somewhere near the fuse box), if you touch 2 or more pins simultaneously, you will blow the fuse. So it's better to have needle probs.

 

The actuators are pretty cheap. I'd say if you'r taking the door card off, just replace it. I ended up replacing one, then bought a new actuator for every door, then I bought more because one broke within a year. They don't seem to last long. I also put the remote key fob in too. Its all real simple once you get your hands dirty.

 

then I bought more because one broke within a year. They don't seem to last long.

Probably because it's a cheap **** from China.
Mines are still good after 17 years.

Again - before changing actuators, just test it with some power supply (I did with a 18650 battery, which is 3.7V). Give it juice and see if it's moving, but try different polarities (but first you have to find out where are + and -, there is total 4 pins, 2 of them are signals)

 

You can get the door actuators brand new for 15quid, I just bought one and changed it, seemed easier than messing about pulling the door apart to test it. Just pay the 15quid throw a new one in and you know it's right. US $18.48 12% OFF|FRONT LEFT FREE SHIPPING 3D1837015 DOOR LOCK ACTUATOR CENTRAL MECHANISM FOR GOLF 5 V MK5 FOR VW SEAT LEON TOLEDO SKODA OCTAVIA|front door lock mechanism|left frontactuator for central lock - AliExpress

 

My t5 sliding door became difficult to open, gradually getting worse eventually I would lock and unlock 3 to 5 times to get it to release. After removing the liner and giving it a spray with WD40 it worked and has done ever since. The central locking cycling and locking problem is according to a mechanic I spoke to common amongst VW, Audi’s he does roadside assistance and told me he has lots of experience in breaking into VWs. I keep my car key on a lanyard and never leave it in the car without the window down if i need to get out for a bit. I thought about investigating whether this could be fixed but VW dealer prices are ridiculous. Cheaper just to keep the key with me.

 

spray with WD40

Better use some grease, which will stay there unlike wd40.

 

Thanks all.
Got the door cards off (not without damage unfortunately - those plastic 'screws' near the lock are a pain!). Got the drivers side lock working again (not sure how - some combination of locking and unlocking various doors). Problem seems to be the signal not coming back from the drivers door indicating it is locked (when locking the passenger door). Any way, to cut a long story short, we just disconnected the wiring so now have manual locking doors - proper retro. Cheers

 

" Problem seems to be the signal not coming back from the drivers door indicating it is locked (when locking the passenger door) "

Check the wires in the bellows....most common fault!!!
Can be up to 15 wires...and 3 or 4 "damaged"!