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mk2

Central locking- the stuff of nightmares...

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Ok everyone, I think I now fully understand the 1997-2011 era VAG central locking system. Same on most VAG cars as far as I know. Please tell me what I've missed!

I needed to sort a lock in my mk4 golf because the rear passenger door lock had deadlocked itself. Nothing would open it. Until I had an idea. Looking at the wiring, the little DC toy motors that operate the locks connect directly to the CCU (convience box). So instead of drilling holes in the door and trying to rip off the door card destroying it, i accessed the pair of wires and simply applied 12v. First the wrong way round, locking, then the other way to unlock. Touched the wires a few times and click whir bang, the door unlocked. i could open it. Hooray!

So, being a saturday afternoon and I needed to use the car sunday, i had no choice except to pull thing out to see if I could figure out what the hell was going wrong with it. No-one locally had a new lock for sale which is my usual easy and quick choice. 

There are 5 microswitches (front locks, with keyhole) or 3 in the rear lock mech (no key sensor). I've figured out what they all do- I think. Completely dismantled the entire mechanism and rebuilt it. The springs are a nightmare. 

Two switches sense if you're unlocking or locking with a key-when you turn it. On front locks only. If one of them isn't working, the central locking won't know that you're turning the key to lock or unlock. So the other doors won't lock or unlock when you turn the key. The CCU wont be aware that you're commanding a lock or unlock operation, so will just sit there and do nothing.

One switch senses when the door is open. This works by cam' ing off the lock hasp- the bit of metal that hooks onto the loop you can see in the door frame. If it is defective, the interior lights wont work when you open that lock (or door), and the CCU will not know if the door is able to be deadlocked (you can't lock a door that is open). It will still try though, which is why you get some odd behaviour sometimes with lock pins popping up and down.

Two more switches inside the mechanism sense if the lock is unlocked, manually lockable or deadlocked. There is a mechanical selector, that is pushed by a cheap little electric motor. When powered it can select one of the three modes. If one of these switches fail, there is no way to know for sure which state, the mechnism is in. Also causing wierd locking behaviour. Banging the door sometimes helps make the deadlocked sensor switch make contact, so you can unlock it again (or apply power directly to the motor...)

If the motor fails in the deadlocked position, there is no way to unlock the mechanism without destroying the door or lock.

I hope it helps someone!

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That’s a nightmare @mk2 , usually this happens at the most inconvenient moment! -at least you had time to sort it.

i understand the door card on the mk4 can be removed with the door shut, but thinking about it the one screw next the mirror would need ripping out - it does not sound fun. 
You can source repair micro switches as a kit off eBay or AliExpress - seems it’s always one switch that goes wrong -same item on Lupo locks too.

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I did a front mk4 door once. No fun. You do have to break everything inside. The only way is to break the card, then bend back the inner metal cover to get to the lock. Once the lock is sorted then you can open the door normally for access and trash the remains of what is left. I believe it cost Vdub a lot of money over the years. Many cars with warranties had lock failures, even the flagship Phaeton had the exact same problems as the cheapest Lupo. And the locking problems continue to show up across the entire VAG range...

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Drill the magic point on a mk4 rear door and you can just pop the deadlock out and the problem will never arise again with minimal effort.

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I also one 'simplified' the whole system, I wouldn't want to do that again.

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8 hours ago, Rich said:

I also one 'simplified' the whole system, I wouldn't want to do that again.

Huh?

I wonder if Lupo doors deadlock and don't open. Never come across one yet. But at least the door cards are easy to remove. One way around the door key switch failure is to fit aftermarket RKE. Cheaper than a new lock mech too.

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I saw Mk4 and dialled out. I'll read again sober.

Imo, Lupos CL systems are awful (primitive) but simple (easy as heck to fix). 

Same systems no?

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