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Old 05-24-2009, 06:51 AM
Junior Member
Join Date: Mar 2009
Posts: 11
Default Driver door won't lock!

I'm the happy owner of a '00 Disco. A few weeks ago during a hiking trip put 300 miles or so on dusty horrible washboard roads. (They were so bad that I lost one of my fog lights! As in it came loose, disconected and fell of my Disco!) Anyways since then the drivers door wont lock when the alarm is armed. All the other doors lock/unlock just fine. The alarm goes off if you open the drivers door. Ithought I got it to the point of being able to manually lock/unlock with the key in the door lock, but today I'm not 100% certain about that either. The inside handle will unlock and open the door, but it seemed very difficult to grab the lock lever,(part that goes up and down), to pull it up to unlock it. I think it's electrical, just cause I can get it to lock/unlock etc. with the key and the handle. I can also feel something like it's trying to send the the signal or something, (when I had the door panel off), and hear it, but it seems like it only gets a faint signal or not the full signal or power. Any idea what it might be? or any Ideas on where to start? Thanks for your help!
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Old 05-24-2009, 07:28 PM
Junior Member
Join Date: May 2009
Posts: 3

I spent nearly all yesterday doing mine. It'd basically lock using the remote but only unlock using the key (interior handle and sill button worked fine but dash switch had no effect). The lock assembly is a large L shaped unit which sits behind the window frame so all of that needs to come out of the door - it sounds harder than it is and in reality only takes about 15 minutes once you've got the door trim panel off. Anyway, that lock assembly divides into roughly two sections; the first one is the door latch itself along with the exterior handle operated lever, the second contains the two motors, cams, switches, lock cylinder geartrain, and levers to control the latch section. On mine, the brushes on the main motor had fallen apart/overheated so the motor ran sluggishly, if at all.

You can separate the two halves, and it is possible to open up the section containing the motors, however it is time consuming, fiddly/mucky to do and if it's the same problem I had, not 100% repairable. Of course, there's the very real risk that if you assemble the two halves together incorrectly the door may not lock at all, or may not release! Ask me how I know...

I was quoted about 75 inc. VAT on Friday from a dealer in Erdington and have to admit that if another lock fails I think I'd just buy another lock rather than go through the hassle I did.

So; on the assumption you're fitting a new lock and want to play with the old one, this is the rough sequence for dismantling - as always, take plenty of pictures on a digital camera to help you when it comes to putting things back together!

1) Remove lock assembly from vehicle
2) Remove torx screw visible below where the lock cylinder shaft enters the assembly and unclip and remove the plastic cover
3) Note the fitting of the white nylon 'arm' near the bottom of the assembly - this loosely connects the spring-loaded black plastic quadrant and the slot in the metal lever. Unclip this arm from the quadrant and rotate anti-clockwise until it can be withdrawn from the slot.
4) Remove the star circlip in the centre of the motor unit and withdraw the securing pin from the rear of the metal bracket
5) Using a blunt old kitchen knife, prise the motor unit away from the metal bracket so that the two plastic pegs are clear of the holes in the bracket
6) Noting how the large black plastic lever on the motor unit engages with the metal levers of the latch unit, pull the motor unit away from the latch unit
7) Remove the torx screws from the motor unit (one obscured by spring-loaded quadrant at bottom of unit)
8) Release the retaining clips (they're very brittle and most will break) and separate the two halves of the motor unit - the geartrain from the lock cylinder shaft spigot has it's own separate cover which needs not be disturbed

Okay, so now you're inside the motor assembly. The motor positioned vertically is the main motor and locks and unlocks the door by raising or lowering the black plastic arm so that it lifts the release lever in the latch assembly out of engagement with the latch itself. The other motor mounted at an angle is the deadlocking motor which turns the spring-loaded black plastic quadrant. This quadrant moves the white nylon arm within the slot so that the interior handle either bears against the release lever(via the peg on the arm) or misses it so having no effect. A peg on the quadrant also pushes the levers into the "lock" position but physically cannot move it back.

The problem most people seem to have, like me, was failure of the main motor so only the deadlocking motor would work, which as described above, locks the door and effectively de-couples the interior release handle. For obvious reasons the deadlocking motor is not operated by the dash switch, only the remote control (the doors being locked/unlocked solely by the main motor from the dash switch). The lock cylinder still works as normal as it operates a 'kicker' cam (the funny shaped white one near the top of the motor unit) via the geartrain and this bears directly on the black plastic lock lever.

The motors themselves can simply be prised out of the plastic unit, however they are not interchangeable - the brass worm gear fitted to each is a different diameter. With care and patience you can bend up the tangs at the end of each one and remove the plastic brush plate and swap them over. You'll also need to inspect the commutator for damage, clear out any carbon deposits, etc. before refitting the brush plate. If you do this, don't put the deadlocking motor back in, it's not essential and you can't afford for it to fail in the deadlocked position!

A brief word on switches. There are three in the motor unit - the top two are operated indirectly by the lock cylinder and simply inform the BCU of key position. The bottom switch informs the BCU that the door is properly latched, the door motors will not run if this is not closed.

Sorry about the essay but I wasn't able to find this info on the web and there seems to be much confusion about how and why these door locks fail so I decided to find out!

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Old 05-25-2009, 09:21 PM
Join Date: Apr 2008
Posts: 77

Nice post and help Darren. I think this will help me to when I encounter this problem. I hope you did some pics so we can know better.

If you ain't first your last!
Wholesale Auto Parts
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Old 05-26-2009, 04:53 AM
Junior Member
Join Date: Mar 2009
Posts: 11
Default thanks Darren

I appriciate the detail Darren. It was definetly not too long. I will give that a shot this week and see how it goes. I'm with Karen - Do you have any pics? That would be very helpful for me! If not I'll do with out. Thanks again for your detailed advice. It will be greatly appriciated.
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Old 05-26-2009, 06:40 PM
Junior Member
Join Date: May 2009
Posts: 3

Sorry, I did think about it but didn't want to get my greasy, dirty mitts all over my expensive new camera; besides, it was gone 10pm before I had the door in a lockable state though not fully rebuilt and after spending all evening and most of the afternoon on it I just wanted to get it back together and get in the bath! Oh yeah, don't know how to upload pics anyway...

I'm sure that with the detail provided somebody will be tempted to take one apart and photo it step by step. Any takers??? Failing that, at some point in the future it will fail again, or a different lock and I'll have a go at taking photos then.

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Old 05-26-2009, 06:40 PM

300c, bcu, discovery, door, doors, driver, forum, land, lock, locks, panels, remote, rover, side, wont

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