Central Locking Challenge, Random locking and unlocking

[dave stewart]

Hi all,
a mate in Australia (Clive) is having a problem with his central locking system. His is the one activated by a remote. The symptom is a random locking and unlocking that seems to have no rhyme, pattern let alone reason. His local mechanic (Tom Dolan from Citromet fame) replaced the motor but the symtom persists. Any suggestions?

[xmexclusive]

Hi Dave

We need to know which model and age Clives car is. Mk1 and Mk2 have very different locking systems.

Regards

XMexc

[Peter.N.]

Agreed. Mk2s have a radio system operating at about 433 mhz and can be subject to interference from any powerful or local transmitter. 433 mhz is within the 70cm amateur band, if you have a local repeater that could cause a problem, plus there are all sorts of unregulated devices that operate on the same frequency, garage door openers etc.

Peter.N.

[UFO]

Clive? I remember a club member named Clive! I wonder if we will see him at a meeting or event at some time in the future? Clive's car is a S1 24V manual.

Nerelle is having the same problem with her S1 Turbo at present and we think we have isolated it to the right rear door. Can't recall how we decided that. I suggested she clean the connectors on the round plug in the door as there may be a short or bad connection there.

The reaction is like trying to lock the doors while one front door is still open.

This post has been edited by UFO on September 01, 2006 02:01 am

[UFO]

Hey Dave, do you think anyone else reads this forum? Are they all still away on summer holidays or so busy fixing their XMs that no one has time to reply?

[noz]

Hi Dave,

There are two things which activate the central locking. One is the Plipper/receiver and the other is a key in the doorlock. To narrow down which one is causing the problem remove the glove box and disconnect the plipper receiver and try the car for a couple of days or however long it takes to show the symptoms. If the problem stops then it has to do with the receiver. If the problem continues then its the mechanism inside the door which is causing the problem.

The most likely cause is the door mechanism or the wiring loom at the door hinge. Somewhere in there there is an electrical short which is signalling to the central locking ecu that a door key is being repeatedly used to lock and unlock the door. To do anything about it you have no choice but to dismantle the innards if the door and check the wiring.

Hope that helps

Cheers

noz

[biffybibophane]

Not sure if the plipper reciever will do the trick, but I will give it a go. The car locks then unlocks using both the plipper and if I use the key to lock the door. Only difference being that if I use the plipper the alarm activates even though the car re-opens itself. The car is so difficult when it comes to locking the doors that even if I push the button down inside the car it pops back up; got to give it points for determination!

I did try and disconnect the wiring on the rear doors but it still didn't resolve the problem.

Cheers,

Nerelle

[noz]

Hi Norelle,

I should have been a bit more specific. You can't operate the central locking from the rear doors because there's no trigger circuit in those doors. In both front doors there is a trigger circuit. This circuit is energised by the use of the ignition key. The microswitch is the only electrical part of this mechanism. However there are many small levers and cams in the lock 'block'. They are prone to seizure because they are in an external environment even although they are inside the door.

If the trigger circuit is siezed then the locks will close under the command of the plip or the key but as soon as they are locked the microswitch which tells them to open again is already made because its siezed. The central locking ecu has no option but to re-open the locks. It sounds to me like the mechanism in the door is siezed or at least sticky. You need to take the door liner of the front doors one at a time starting with the drivers door and free off the trigger mechanism.

I will warn you that it won't be easy. Access is very limited. Be sure to have a swear box nearby. Can I suggest that the best way would be to remove the lock 'block' entirely from the door and un-sieze it on the workbench?

This is a common XM fault but one of the easier ones to solve.

Please let us know how you get on.

Cheers

noz

[UFO]

AH! Thanks Noz, that makes heaps of sense!

[Norman]

Hi all,
Now for the door locks unlocking after being locked, by disconnecting each door in turn by unscrewing the harness connector at the door end i have found the problem to be the passanger door at fault looking at the corroded connector and thinking a little WD40 will cure that but no such luck time to dismantel the door and look at the switch.
Dismantled the door and removed the lock assy all free as a bird disconnected the wiring and the other three doors lock and stay locked recannected the plugs and the doors opened.
after a few experiments it seems the door lock command is a pulse from the switch and not a permanent closed contact switch as linking out the contacts caused the door lock not to recieve a command to operate, went to the scrap yard to obtain a replacment lock assembly but no difference same symtoms as before the motor and switch assembly is a sealed unit which looking at it will not go back together i will be opening today to see exactly have it works.
I will keep you posted with what i find.
Regards,
Norman

[Norman]

Hi all,
Dismantled the replacment door lock as it sounded ropier than the original (this is a destruction job it wont go back together) checked the operation of the assembly by plugging it back into the door harness the motor ran freely but the linkage to the switches diden't £35 down the drain for a defective door lock from the scrapyard and it was the only mk1 lock there all the others were fitted with different connecters and are not interchangable (plugs wired differently and different fixing clips) Armed with the knowledge of what the swithes did and Nos's central locking circuit i simply left the four way plug disconnected reconnected the two pin motor plug and hey presto Central locking on all four door the only thing missing is the display which shows the passenger door is open but that i can live with.
Regards,
Norman