How to change a door lock mechanism

Opening the passenger door on my MGF 1.8i failed to activate the courtesy lights – not that big a deal but it also means that the alarm, if set, is not triggered. The fault lies in a micro switch within the door lock mechanism which in effect is a sealed unit so the solution is to replace the mechanism and fortunately used parts are available for under £20 (make sure you get the right one – driver’s & passenger door parts are ‘handed’ so are not interchangeable and you do need one from a car with central locking).

The mechanism is quite a complicated bit of kit. It has an electrical connection (5 wires in a plug) and 3 mechanical connections – one each for the external handle, the internal handle and the door pin. The mechanical connections are shown here




The internal handle fittings are easier to see when the mechanism is rotated through 90 degrees as fitted to the passenger door (with the front of the car to the right)



To remove the old fitting, first remove the door card then carefully peel forward the clear plastic liner that you should have fitted to prevent the door card getting damp. Work with the door open. With the fitting in-situ undo the external handle clip first.
This shows the clip….you need to pull it off the rod which will then pop-out of the centre of the red clip.


After that I found it easiest to disconnect the electrical plug by pushing the fir tree fitting in to the door and pulling the plug. Next, undo the 3 torx T25 ‘bolts’ that hold the mechanism in place:


With the unit loose, undo the internal handle at the mechanism end. The outer cable is held in the clip and the working end has an ‘s’ bend which you can wiggle out. This shows the cable after removal.





This shows the clip and the hole for the ‘s’ fitting.

Next you remove the whole unit complete with the door pin by dropping it down and more wiggling. Note where the door pin exits the door normally before you do this! This then gives you the old unit with door pin fitted thus:



Wiggle out the door pin.
As always, fitting is the reverse! Fit the door pin to your new unit. Wiggle the whole lot back in to the door with the door pin emerging from its correct hole. At this point it is best to refit the external handle connection, then the internal handle connection then offer-up the fitting and refit the 3 torx bolts. Finally, re-connect the electrics and push the fir tree connector back through its hole.

Re-fit the plastic liner (sellotape) then the door card. Job done!

Nice one! :broon:

Pefect how to! Thanks buddy!

great piece of work - extremely helpful - managed to do the lock in a few minutes