Central locking fault

[Dickie Dastardly]

My 1999 Chim developed an intermittent central locking fault over the weekend. When the remote fob is pressed the indicators flash and the alarm sets, however the central locking mechanism does not operate, strangely though when the fob is pressed again to disable the alarm you can hear the solenoid make a noise as if it's trying to retract - even though it never actuated in the first place.

I have checked the multiplugs on both central locking solenoids; removed, checked and oiled the door switches in the sills (which were fine [the interior light works perfectly]) and disconnected/reconnected the battery to try and reset the alarm.

When sitting inside the vehicle and trying to lock via the button on the door opening knob you can hear a relay clicking behind the dash!!

Does anyone have any suggestion on a possible cause??

Thanks
Richard

[Ribol]

Does it lock via the knob button but not via the alarm remote or neither?

[Dickie Dastardly]

Symptoms are the same from both unfortunately, it might lock every one in twenty attempts!

[Ribol]

Assuming the connections to it are all ok it sounds like the C/L relay could be on its way out.

The alarm and the knob button energise the C/L relay the same way so if they are both playing up that would suggest the fault is at the relay.

Does it unlock ok every time?

[Dickie Dastardly]

It seems to unlock fine; also when testing the system the central locking solenoids try to retract upon disarming the alarm (though since the car didn't lock in the first place they were not actuated/extended). It suggests to me the wiring seems ok. When sitting in the car and trying to lock via the button on the door opening knob I can hear a relay under the dash clicking every time the button is pressed.

I hope this explanation is not to confusing!

[Ribol]

It is highly unlikely the door solenoids would both unlock ok but mainly not lock ok.

If you use the knob button the relay clicks but doors don't lock so that would suggest the button wiring is ok.

If the same can be said when you try using the remote from inside the car that would suggest the alarm pulse is there at the relay.

I would check all the connections at the relay just to make sure in a final effort but I would say what you have a relay on its last legs.

(all IMO and usual disclaimers apply )

[Dickie Dastardly]

Thanks for that, any suggestions are very welcome (and disclaimer fully noted)

[SMB]

Ribol said:

It is highly unlikely the door solenoids would both unlock ok but mainly not lock ok.

If you use the knob button the relay clicks but doors don't lock so that would suggest the button wiring is ok.

If the same can be said when you try using the remote from inside the car that would suggest the alarm pulse is there at the relay.

I would check all the connections at the relay just to make sure in a final effort but I would say what you have a relay on its last legs.

(all IMO and usual disclaimers apply )

I've just replaced both door motors after a failure of the locking system, checking wiring and substituting the CDL relay made no difference to mine. My fault was a complete failure of the car to lock or unlock either from the button or the alarm. If i moved a motor slightly I could perhaps get a single movement, but that was irregular.

Everyone says it's unlikely both motors could fail but mine did!, It was checked just a week before when it passed it's MOT. neither the CDL relay or the motors are expensive, so worth having a spare stock to do part substitution, as an auto electrics expert will cost you more in a call out alone.

Replacing the motors fixed the problem.

[Harrytsg]

I had exactly the same problem a couple of months ago, the fault was a dry solder joint on the 'lock' coil of the relay, the relay (on mine) is the large one next to the alarm module, under the dash on the far left (passenger side). The relay has 2 coils (thats why its larger) one for lock the other for unlock, it was an easy fix to resolder the coil leg.
If you lift the dash you should at least be able to 'feel' both coils clicking, that way if its not the relay you can eliminate it eliminate it assuming its other connections are ok.

If i can find a picture i will post it up.

[Dickie Dastardly]

Thanks for the advise; dash top off at the weekend me thinks.
Will update the post with any findings.
cheers

[Dickie Dastardly]

Took the dash top off yesterday which was suprisingly easy. Found that the CL relay while clicking was not making full contact, by removing the relay shroud i could operate the points by squeezing the contact by hand (the relay has two seperate points within the same casing - one for locking and one for unlocking), a good blast with WD40 seems to have done the trick.
Thanks for the comments/suggestions posted, they all help when doubt is creeping in!! (also spoke to Carl Baker on Thursday who couldn't have been more helpful)
Cheers