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Central Locking - Security or Safety?


Ady_E
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Hi all

I have recently been experiencing problems with my Central Locking system. Two of the doors (passengers and rear nearside) fail to 'safe' (according to vag-com). After much research I now know that 'safe' means 'deadlock'. Once a lock is 'safe' it can not be unlocked or opened from the inside also. I have checked this is true by locking the car with the windows open and attempting to open the doors using the internal door handles. Sure enough, the two door mentioned can still be opened from the inside while the others can not.

The arrangement inside the lock assembly is shown in the first attached pic. There are two separate motors, one controls the Locking and Unlocking and one brings in a mechanical interlock that, once 'locked', prevents unlocking unless it is first 'De-safed'. The second pic shows the unit in the 'locked' but 'unsafe' state. The third in the 'locked' and 'safe' state.

The problem I have is the better of two scenarios involving this 'safe' motor. The first is that it fails to 'safe' in that it won't deadlock the door. The second is far more worrying. It won't 'De-safe'. This means that it won't remove the interlock preventing the unlocking of the door. This essentially means that the door can not be unlocked or opened by any means.

My question is simply this, at what point was security allowed to take precedence over safely?

A door that can not be opened by any means can have grave safely implications. Manufacturers, including Audi, have gone to great lengths to include a feature that automatically unlocks all door in the event of an accident. However, if the 'safe' motor in the door lock assembly has failed in the 'safe' position, this door will NOT unlock as the interlock is mechanical, controlled electrically and can therefore not be overridden.

I asked Audi about this and they couldn't give me an answer. Worrying? I think so. What do you think?

Incidentally, if anyone is experiencing similar problems and you have the engineering ability and time, the 'safe' motor can be exchanged for a similar one available at Maplin Electronic (Cat No. YG13) at a cost of £2.79 each. A new lock unit from Audi is between £111 and £116. I haven't tried swapping the motors yet so please don't quote me on it and the existing internal 'wiring' arrangements (metal strips!) will need a little modification to make them fit.

My motors do actually work when applying a voltage directly to them (after a refirb) but won't work from the Central Locking Control Unit. Having checked the voltage output from the Control Unit as being correct I was left with one question, Is the Control Unit faulty (as I have problems with multiple doors) or have both lock assemblies suffered the same failure?

I was able to answer this by tracing the wiring back to the control unit, removing the cover to reveal the pin out of each connector only to learn that the controller controls two doors from same pin on the circuit board. In my case the two rear door safe motors are wired in parallel and that, because only one rear door is affected, it can not be the controller. Happy Days! :D

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For there to be a problem you need two "failures" - the safe motor failing in the "safe" state (since you have two failures and they are both in the non-"safe" state you have to conclude that the risk of that happening is very low) AND for you to have a crash. Most risk analysis only considers the effect of single unrelated failures so this is not a situation that would be taken into account.

Plus I guess that purchasers of a new car worry more about how secure it is (i.e. how likely it is to get stolen) than they do about what will happen in the (they hope unlikely) event of an accident.

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For there to be a problem you need two "failures" - the safe motor failing in the "safe" state AND for you to have a crash.

Your absolutely right Dave. I wasn't concerned about my own situation as my dodgy locks both fail to safe. I do have a friend with a VW who has a door that occasionally fails to de-safe, and therefore unlock. It's this situation that can be potentially hazardous.

An accident, by definition, is an unplanned and unforeseen event that leads to injury or damage to property or the environment. However, being a qualified Risk Assessor, in my experience, accidents are usually as a result of several errors combined together. Seldom is a accident caused as a result of a single error or 'failure'.

Plus I guess that purchasers of a new car worry more about how secure it is (i.e. how likely it is to get stolen) than they do about what will happen in the (they hope unlikely) event of an accident.

No-one ever worries about how 'safe' their car is until it's too late to worry about it. But, perhaps they should be. In 2005 less than 200,000 cars where stolen while there were 258,000 casualties as a result of motor accidents in 2006.

I don't want to be seen as a scare mongerer, I just don't want to hear that someone somewhere couldn't get their kids out of their burning motor because the doors wouldn't unlock following an accident! Extreme? Yes, but that is worse case.

Ya never know maybe it'll be the car thief that'll be stuck in a burning motor unable to get out! lol

Thanks for your input.

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When they're peeling the roof off your car like a tin of tuna after a serious accident, I can't imagine the first thing that springs to mind is likely to be "damn it, my rear offside door didn't de-safe."

I think you really are looking into this too deeply.

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OK. Point taken.

I still beleive there to be potential hazard brought about by car manufactuers (not just Audi) putting security before safety.

If readers want to ignore this possibility, however slim, that's up to them.

The insight of how the lock assemblies work and possible repair solution still stands though. Some might have use for it.

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Modern life is all about assessing risk and taking appropriate actions.

Taken too far assessing risk takes over your life, I think that's what we're trying to say to you. There are many more far riskier things that we all do every day, so on the list of "risks to worry about" this doesn't even make it into the top 100 IMHO.

P.S. I'm a qualified Risk Assessor too. One of the things I learnt about applying risk assessment is to tackle ONLY the top 6 risks at any one time and resolve them, taking on more than that means that you end up reducing none of them due to diluted effort.

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Incidentally, if anyone is experiencing similar problems and you have the engineering ability and time, the 'safe' motor can be exchanged for a similar one available at Maplin Electronic (Cat No. YG13) at a cost of £2.79 each. A new lock unit from Audi is between £111 and £116. I haven't tried swapping the motors yet so please don't quote me on it and the existing internal 'wiring' arrangements (metal strips!) will need a little modification to make them fit.

OK I have changed the dodgy safe motors for the ones stated above. Physically, they fit like a glove but electrically, they are reverse polarised compared to the old ones. All this means is that you'll need to cut back the metal strips and solder wires to the motor and reverse them as shown in the picture. This ensures that the motor rotates in the correct direction otherwise the lock will 'safe' when you try to unlock the car! Not good!

I have also learned that if there is a problem with the any of the central locking motors it can be heard when locking/unlocking the car. The controller has a second attempt at locking, safing, de-safing or unlocking if the first attempt fails. If, for example your car sounds like it is trying to lock itself twice (as mine was), it's your first indication that there's a problem. If the doors are locked it just means one or more lock has failed to safe (deadlock).

£230 saved from the stealer's pocket! :grin:

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