Central Locking Gone Again

[MGTF_avengers]

Right, this is now getting rather annoying.

In case anybody didn't read previous posting on this - they were dotted around on different threads,
ever since October/November last year, the alarm on my 2010 TF has been randomly going off, culminating on New Years Eve on the central locking packing up as well.

If I pressed the lock button on the fob - nothing! No lights flashing no latches dropping, no click. If I press the unlock button, I hear a click, but the latches are already in the up position so other then that, nothing happens.
If I press lock on the fob and then open the door, the alarm goes off - so it is set, just no central locking or flashing lights (but then it will randomly go off if when left).

So I took to dropping the passenger latch, and then locking the driver door with the key.

Took it in to my nearest MG garage on the Monday, towards the end of January. They said the actuator in the door had gone, so fitted a new one. Worked OK when I picked it up on the Friday. Worked OK when I locked it when I got home. The next day, the central locking had gone again.

Rung the garage Monday, they couldn't fit me in while the next Monday. Took it back then (and also pointed out to the mechanic working on my car it could be the wiring loom into the boot lid), on collection the following Friday (8th Feb) they said it was the actuator in the door - the replacement was faulty, so they put another new one in. Once again, worked OK when I picked it up, and again when I got home. Worked OK through Saturday as well.
This morning however (Sunday), I heard the alarm going off again. Oh no, not again......
Yes, the central locking has gone AGAIN!

Looks like another phone call Monday morning.

Am I right, could it be the wiring loom into the bootlid?

[mgnminiman]

It might be caused by a faulty relay in the alarm/bcu unit? These are known to fail on older cars.

If they connect it to the T4 diagnosis equipment this should tell them where the fault lies.

[Rob Bell]

If a relay had failed, then it is odd that it is so intermittent. In my experience when a Pektron relay fails, it does so in a binary fashion. In other words when it dies, it's dead. That doesn't sound the case here?

It seems equally odd that you've been through three lock mechanisms in short order. Clearly something is not right: is there a short through the lock to burn it out? What was the actual problem with the previous mechanisms?

[MartinW]

I have had three lock actuators replaced on my LE500 but over a 12 month period. On the one occasion it was thought the actuator had become sticky when I had sprayed Waxoyl in the doors, but on the other two occasions it was definitely faulty units which I am told and from experience can confirm will start to show up as an issue when you hear a rattling in the door.

I was also able to lock the passenger door by pushing the button down and then using the key to lock the drivers door and then unlock both with the fob, but unable to lock with the fob as you describe.

A few LE500 owners have had a similar alarm issue but not everyone has suffered this problem from what I understand. I was told that the actuators were reverse engineered and were Chinese sourced and consequently weren't to the same standard as originally. Apparently the mechanism becomes stiff (possibly from water ingress) and so one fix was to protect the unit with grease, but this clearly didn't work in my case nor in yours.

It would seem that if the voltage drops below a certain point the alarm goes off, but I don't know if this then causes issues with the actuator being able to lock the door, or whether it is the other way round that the actuator being unable to work causes the alarm to go off, but like you my problems have always started with the alarm just going off and then discovering the problem of it not locking. Currently mine is rattling again so I am expecting a further replacement.

As to the boot loom causing the problem, I don't know if this is the case, my loom looks ok around the stress point.

The door actuators, and the short life of the coil pack rubbers and track rod ends does worry me, though and I doubt I will keep mine much beyond April when the warranty is finished.

[Rob Bell]

Might be better to fit a s/h MG Rover part instead? Or are MGR OEM locks still available from X-Part?

They (original MG Rover latches) are still available new it seems - but rather expensive: http://www.rimmerbros.co.uk/Item--i-GRID000122

[MGTF_avengers]

Thanks for the thoughts guys.
I've booked the car in on Monday 18th.
if the actuator is not to blame. Wouldn't fitting a MG rover one instead of another Chinese one make no difference,as something else is causing it to fail and therefore the MG Rover one would fail also.

[Rob Bell]

What Martin is saying is that the Chinese door lock mechanisms are not of adequate quality - so could fail quickly. MG Rover ones are not entirely problem free, but at least seem to last 15 years before causing problems. But yes, if it isn't the door lock, and the problem lies else where, then replacing with another lock is not likely to resolve the problem.

We really need to understand why three door locks on your car have failed in short order. If the approach is to discard and replace, then we may never know what the original problem was!

[austingarages]

If a relay had failed, then it is odd that it is so intermittent. In my experience when a Pektron relay fails, it does so in a binary fashion. In other words when it dies, it's dead. That doesn't sound the case here?

It seems equally odd that you've been through three lock mechanisms in short order. Clearly something is not right: is there a short through the lock to burn it out? What was the actual problem with the previous mechanisms?

Agree completely with that! Every SCU I have encountered in the past the relays are an outright failure and never intermittent.

There may well be a problem with the loom here, replacing a door latch simply disturbs something to temporally cure the fault.

It is worth pointing out here to read the alarm trigger store - diagnostics will recover the last 4 occasions as to what set the alarm off and will hopefully point them in the right direction. In Pektron SCU talk "unknown trigger" indicates a wiring short - no doubt the boot hinge area or even behind the centre console in the area of the SCU.

If the there is a problem with the door latch or loom to it, then the SCU will wait for the confirmation signal that the door is unlocked via the micro switches inside it, therefore it will not operate the "lock" sequence because it does not know the door is "unlocked"! A simple test is to disconnect the main battery briefly (which will interrupt the sequence) and then see if it locks - it should do once, then pack up again....

[MGTF_avengers]

This Pektron relay.....
I assume it unlocks the doors - i.e. : operates the unlocking mechanism and fires the latches on the doors up, so you can open the doors.
If so then I can categorically say the Pektron relay hasn't failed, or I wouldn't be able to open the locked doors with the fob (which I still can do).

I still think it's the boot loom.

[austingarages]

This Pektron relay.....
I assume it unlocks the doors - i.e. : operates the unlocking mechanism and fires the latches on the doors up, so you can open the doors.
If so then I can categorically say the Pektron relay hasn't failed, or I wouldn't be able to open the locked doors with the fob (which I still can do).

I still think it's the boot loom.

The Body Control Unit (BCU) or Security Control Unit (SCU) made by Pektron has 5 double relays. On the TF they control the horn, rear fog, window up, window down, door unlock, door lock, deadlocking and intermittent wipe.

A failed relay would not give you the trouble you are having (replacing the latch cures the fault for a while).

A failed boot loom would more than likely set the alarm off without any pattern - but would not cause the car not to unlock or lock unless it blows a fuse.

If the boot light still works (including the warning for it open with the ignition on within the instrument pack) along with the remote boot release (if fitted) and the centre stop light, then the boot loom is likely to be intact.

The key to this problem is to read the alarm trigger store memory and work from there. The alarm going off without pattern can also be caused by dodgy latches and/or wiring to them. Try a battery reset as suggested earlier and see if the CDL works after that (the CDL will work only once!), disconnect the negative lead for 5 seconds is all that is required.

[colintf]

many thanks for sharing your knowledge again Nick and Jean

[MGTF_avengers]

Try a battery reset as suggested earlier and see if the CDL works after that (the CDL will work only once!), disconnect the negative lead for 5 seconds is all that is required.

Thanks Nick & Jean, will try this tomorrow and report back!

[MGTF_avengers]

Right - battery reset done.

On pressing the 'lock' on the fob, the central locking did indeed work, however there were no flashing indicators (i was expecting to see the flashing lights).
Pressing the 'unlock' worked as it always has.
Pressing the 'lock on the fob again - nothing.
So you were right Nick & Jean, it worked only once.

By the way - regarding the boot loom issue.
I have always been able to unlock the boot with the fob, the boot light is working (always has), the bootlid brake light is working, and the 'boot open' indicator on the dash is working too....
So does that indicate it isn't anything to do with the boot loom then?

[Rob Bell]

Good chance the boot loom is fine. And on such a young car, it was a rather unlikely cause, but you can never be sure.

If the there is a problem with the door latch or loom to it, then the SCU will wait for the confirmation signal that the door is unlocked via the micro switches inside it, therefore it will not operate the "lock" sequence because it does not know the door is "unlocked"! A simple test is to disconnect the main battery briefly (which will interrupt the sequence) and then see if it locks - it should do once, then pack up again....

Looks like a loom or mechanism fault then. Which might fit with what Martin has said about water/damp ingress into the Chinese manufactured locks. But I'd want to be sure that there wasn't a loom fault before replacing the lock mechanism again.

[MartinW]

I have just talked to the service manager at my local dealer. He says they keep a few in stock for the NAC TF because they're prone to failure. He says of all the ones they have done, only one has had the opposite problem of the car refusing to unlock and that was the BCU as detailed above. In the case the more common failure the micro-switch is prone to failure and that they do attempt to keep the water out when fitting them. The fact the alarm goes off is related to the micro-switch failing apparently.

My last unit was fitted 12 months ago so, but as to whether the older MG Rover units fit is not known as being a dealer they just fit replacement units under warranty.

[MGTF_avengers]

I have just talked to the service manager at my local dealer........the micro-switch is prone to failure and that they do attempt to keep the water out when fitting them. The fact the alarm goes off is related to the micro-switch failing apparently.

I can't see how water would be getting into the mechanism while they are fitting the unit, Martin - all the work is done inside.
I think then, logically it would be a problem with the loom that goes to the locking mechanism.

In which case (looking back at Nick & Jean's posts)if my garage hooked the car up to the T4 diagnostic equipment, and read the alarm trigger store they should see, in Pektron SCU talk "unknown trigger" indicates a wiring short.

......but I'd want to be sure that there wasn't a loom fault before replacing the lock mechanism again.

I'm with you on that one Rob.

[MartinW]

This is a bit like the reverse parking sensor on the LE500, I think. These were prone to going off in the rain as a continuous beep. The first fix was apparently to tape over the connector block to prevent the water getting into the plug. However, it would reappear as an issue. In the last 12 months mine has behaved impeccably because the cure now seems to be to cut back the wiring from the plug and then have the sensors hard-wired directly to the controller in the boot. The reason it seems this fix works is because the loom still has moisture in it when just taping over the block. However, by cutting it back you get rid of the piece of the loom near the plug that has moisture trapped inside the insulation and by hard-wiring with plenty of heat-shrink to cover over the new joint, it solves the problem.

Consequently I wonder if the problem is moisture in the wiring loom to the switch, made worse at this time of year (which is when mine generally failed) with the moisture and lower temperatures causing condensation and problems of shorting?

[Rob Bell]

Have they under-specified the connector? Plenty of good-quality water resistant/proof electrical connectors available - and can even be had off ebay. Not that that helps in the case of the door locks, which will have a dedicated loom connector (short of cutting off the existing ones and replacing them!)

[austingarages]

Have they under-specified the connector? Plenty of good-quality water resistant/proof electrical connectors available - and can even be had off ebay. Not that that helps in the case of the door locks, which will have a dedicated loom connector (short of cutting off the existing ones and replacing them!)

I have just talked to the service manager at my local dealer. He says they keep a few in stock for the NAC TF because they're prone to failure. He says of all the ones they have done, only one has had the opposite problem of the car refusing to unlock and that was the BCU as detailed above. In the case the more common failure the micro-switch is prone to failure and that they do attempt to keep the water out when fitting them. The fact the alarm goes off is related to the micro-switch failing apparently.

It sounds very much like any of the above, most likely a large batch of dodgy latches with micro switches failing.

If the latches (microswitches) are faulty and the alarm is going off, the the alarm trigger store should read "Drivers sill up" or "Drivers sill down" depending which way round it has failed.

The MG Rover latches were made by Aditya Auto and fresh stock supplied by Xpart is stamped manufactured October 2007...

[MGTF_avengers]

Just to update,

I have picked the car up from the garage today (Saturday 23rd).
It's working again, however I have not been able to talk to anyone there about what work has been carried out this time around.
Andy, who works in the showroom area, and whom I dealt with had already gone home, and couldn't be contacted at the time.
Walking to the car after picking the keys up, I saw one of the mechanics. I asked if he knew who had been working on my car - he did, but he had gone home as well.
So I filled him in as to what was going on, and asked if he knew what had been done. He said he thinks they replaced the door actuator again!

Well this didn't fill me with a whole lot of confidence - and I told him it's highly likely it will go again if indeed this is all they have done.

I'll ring Andy on Monday and report back.

Like I said at the start, for now it's OK.