ALSO Refer to Shop Manual Schematic Page M:18:14
The Locking Mechanism in the gullwing doors of the DeLorean are slaved to each other through a central locking system. This system is configured such that a change in the lock/unlock status of one door will be duplicated in the other door. This occurs when either door is locked/unlocked either from inside the car or with a key from the outside. There is no separate Lock/Unlock switch, and no factory provision for a remote keyless lock control.
This synchronization is accomplished by a Door Lock Control Module that pulses a large, bi-directional solenoid in each door. The solenoids are tied to the lock mechanism of the doors. A wiper switch (bell crank) monitors the position of the mechanism in each door and controls the Door Lock Control Module to direct the pulse to the solenoid in the direction it needs to go. If the central locking function appears to work intermittently, it is possible that the wiper switch is damaged or out of adjustment.
CAUTION Never operate the door locks with doors open, only when both doors are closed.
Common problems are:
A. Solenoid Failure
B. Lock Module (pulse unit) failure
C. Door Latch wear
D. Other issues with binding/adjustment in the mechanism, Wiper Switch alignment.
A. Solenoids are easy to replace (once you remove the interior door panels). The only hitch is that DMC has only (Left Side) LH solenoids P/N 100861. They must be physically turned around to work in the passenger side. To use the LH unit on the right side (RH) of the car, you can either open up both units and swap the internal parts, or bend the mounting bracket on the new solenoid to the correct orientation. Either option is fairly obvious with the new unit in hand.
B. DMC offers a Digital Door Lock Control Unit (Lock Module) P/N 101421. Microprocessor controlled, it is much more positive and reliable than the old relay box. It includes indicator lights that can help diagnose other problems and will automatically back off the lock function in the event something jams inside a door. This will save the solenoids and the car battery! This new controller can also accept input from a Remote Keyless Entry P/N 111421, which is easy to install.
C. There are two Door Latches on each door. The Front Latch P/N 101666 for the left door is the same part as the rear latch for the right door. The Rear Latch P/N 101665 for the left door is the same part as the front latch for the right door. There is a kit of all Four Door Latches available as P/N K111665.
As the latches age, they become sloppy and often don't reliably close all the way. This causes the familiar "hang" of one latch, usually the front, when trying to open the door. For a while, liberal lubrication with WD-40 or the like will alleviate this tendency, but sooner or later it will be time to replace the latches. Avoid using heavy grease in the latches as this just attracts dirt and makes them worse. Often simply cleaning out old grease from the latches with some brake cleaner will help door latching issues.
D. In order for the latches to lock, the door must be closed and the latch set internally to the correct position. When replacing the latches, and sometimes just as parts age, it is necessary to perform the Lock and Latch Procedure outlined in the Workshop Manual P/N P3113096 page P:02:11. This procedure will align the components in the door and will also align the wiper switch to ensure proper operation.
Revised 6/30/2016 DAS [added detail]