The following tutorial on the door lock actuator was written by KevLar on DiscoWeb.org. He also provided pics to help explain a crucial important issue with determing the polarity of the replacement motor. The following was based on his 96 Disco. Land Rover Discovery 1 (1996) - Power Door Lock Actuator Motor Replacement Tips If one of your doors is not locking and you have determined the likely cause to be a failed actuator here are tips for diagnosing and replacing the motor. First, before removing anything, check that the actuator is the problem. Close all doors except the problem door and press and hold the courtesy light button of the open door to fool the Central Locking System (CLS) into thinking the doors is closed. Place your ear on the inner door panel about 6 - 8" below the lock pull tab and listen carefully for any sound while pressing the LOCK button on the key fob, repeat while pressing to UNLOCK. Do this as many times as you need to in order to confirm that there is no sound coming from the actuator inside the door. If you do hear noise then you either have a lock linkage problem, or the motor inside the actuator is trying to turn but does not have enough power to operate the locking linkage. If you've confirmed that you have an actuator problem, the next step is to remove the inner door panel and peel back the vapor barrier in the area below the door lock pull tab to expose the actuator mounting plate. With the actuator mounting plate exposed, unbolt it from the door. Then, disconnect the short metal rod linking the end of actuator shaft to the door locking linkage, making sure to note how it was hooked into the actuator shaft. With the actuator still plugged into its power harness, press down the courtesy light button again and repeat the LOCK/UNLOCK procedure with the key fob to see if the actuator is now working. If the actuator shaft moves, then it is likely that the motor has enough power to operate the actuator by itself, but not enough to operate the door lock linkage. To ensure that your actuator motor is in fact the problem, check the door lock linkage by pulling the lock tab on the inner door and by using the key on the outer door. If the linkages move freely, try operating the door lock by pushing/pulling on the short linkage that you just disconnected from the actuator. Checking these 3 input points of the door lock linkage will confirm that the linkage is operating without binding or jamming.At this point, you have determined that the likely problem is the actuator motor. Disconnect the actuator power harness and cut any tie wraps needed to remove the plate with the actuator attached. I suggest that you also remove and set aside the short linkage that you disconnected from the actuator because it may fall off and through a drain hole in the door bottom and get lost. With the actuator removed from the truck, remove actuator from its mounting plate, taking note of how the actuator was mounted on the plate. You should take pictures or make sketches of the orientation of the various parts before you remove or disassemble them from the door. Then, follow CandiMan's instructions and open the actuator casing. With the actuator casing opened, you should check if the motor works at all when power is applied directly to its contacts. Use a 12V DC power supply or the battery itself to give a short burst of power to the motor. It doesn't matter which contact you apply the and - 12V to, since you are just checking to see if the motor works. If short contacts with 12V power do not make the motor turn, try turning the large white nylon gear that meshes with the motor gear about 1/4 turn which will move and reposition the rotor inside the motor. Now try applying power again. If the motor works, it is likely damaged or has some dirt or corrosion inside. You can try to clean the inside of the motor with liberal sprays of WD-40, but I tried this and although the motor would turn and move the actuator shaft on its own, it could not generate enough power to operate the door linkage ! Assuming you have managed to find a replacement motor (eBay, RC shop, etc.), keep following CandiMan's instructions for motor replacement. When you reach the point of connecting the two wires to the motor itself, you MUST confirm that the polarity of the replacement motor you are using is the SAME as the stock motor ! I made the mistake of assuming the new motor I had was the same as the stock motor, and when the "repaired" actuator was put back in the truck, the locking system would go into a tizzy and set off the alarm but would not lock the doors. It turned out that the replacement motor which appeared exactly the same as the stock motor and was made by the same manufacturer was in fact reverse polarity from the stock motor... When all the other doors were locking, the repaired actuator was doing the opposite, and the micro switch inside the driver's door actuator was also sending a conflicting signal to the CLS, which detected the problem and sent the locks into a tizzy. So, before soldering the leads of your replacement motor, carry out the following test. Apply 12V DC to one contact of your motor and ground the other contact. Note the direction the motor turns while looking at the geared end of the motor (see picture). Determine which motor connector makes the motor turn CLOCKWISE when 12V DC is applied to it. That connector is the one that you MUST connect to the PINK wire !Finish following CandiMan's instructions. If you intend to use epoxy to seal up the repaired actuator casing, I suggest that you perform a final check before permanently sealing the unit. Temporarily secure the two halves of the actuator casing tightly together with a couple of large hose clamps, tie wraps or small shop clamps. Plug the actuator connector back to the door harness without mounting it to the door. Then press and hold the door courtesy light button as before, and press the LOCK button on the key fob. The actuator shaft should move OUT. The shaft should move IN when the UNLOCK button is pressed. With this final check of proper operation, you can now proceed to permanently sealing the actuator casing with epoxy.