Unlocking the mystery of DeLorean Lock Modules.

There are a lot of known issues with the DeLorean DMC-12 and so many of them are electrical in nature, like many other cars with Lucas electronics. 

That old gag.. Stolen from the internet

I am unsure who would get credit for the DeLorean Lock Module (DLM) design, although some boards are marked "Diamond H Controls LTD". It is fairly simple and effective for late 1970's "mass produced" electrical engineering but it leaves a lot to be desired by modern standards. The purpose was to have central locking so when either door was manually locked or unlocked, the other door would do the same. There are no lock/unlock user operated buttons or switches (like newer cars), it is all done with the mechanical lock. 

Each door has a switch that connects a signal wire to ground based on the position of the door. The action of a wire going from open to ground triggers the DLM to briefly energize both door lock solenoids and move the locks in the desired direction. That is the function of the DLM. 

There are a number of mechanical reasons the door locks can fail, but that is not the purpose of this discussion. Instead, I will focus on the electronics behind it. If you are trying to troubleshoot your locks, make sure all of the physical stuff is working properly before proceeding with the electrical stuff. 

DeLorean door lock solenoid

Many of the stock modules fail because the relays get stuck closed. It is likely because of the spark created by the rush of current the solenoids need to activate. When the relays stick, the solenoids stay energized and should trip the thermal breaker. When the breaker resets itself, the solenoids are energized again, and the cycle repeats until either the coil fails or the battery in the car is dead. Typically, when this happens, the solenoids will need to be repaired or replaced (it is possible to re-wind them with new wire). 

Lockzilla module sold by PJ Grady

In the early days, some of the vendors sold replacement DLM to address the problem. LockZilla, sold by PJ Grady, (I have one for sale, contact me if you want it!) was very popular. There was a less popular module sold by the now defunct DeLoreanOne, where the board fit in to the original DLM housing. Both designs address the problem by using relays rated for higher current, but seem to use the same design as the original DLM.

DeLoreanOne module (photo from Elvis)

One of the primary safety flaws I find with these designs is the lack of proper fuse protection. The module is powered through the 9 pin RISTS connector (purple wire), and it is fed directly (electrically) from the battery. It has unfused power all of the time. The thick red wire connecting the thermal breaker only provides power through the relay to the solenoids. While the thermal breaker is some form of protection, it is inadequate, as I describe above. Many people unplug just the thick red wire on the DLM, thinking they are disabling it, but the 9 pin RISTS connecter also needs to be disconnected to stop the 12mA idle current draw. 

Way back in 1997, in the days of the DeLorean Mailing List (DML), Dave Swingle shared some board layouts and schematics that he generated himself. It contained some errors but did a good job of demonstrating how it all worked and provided a good first step to people like me that would later work on solutions to the problem. 

Some years later Elvis Nocita published instructions for an "upgrade" to the stock module that changed the transistor to a modern high-gain one and adjusted the resistors in the circuit to reduce the idle current consumption from 12mA to 1mA. Elvis also fixed the fuse protection by replacing the thick red wire with a 20A fuse and eliminating the purple wire. It also required that the old worn relays be replaced. I believe Elvis still provides this service to owners, as does DeLoreanGo. I can also do this update to your stock DLM, feel free to contact me (especially if you are in the USA). 

While some people are opposed to it, many have replaced the old heavy lock solenoids with modern lightweight plastic actuators that use a small DC motor to move. It is not clear to me what the controversy is, but I have had excellent results with the actuators and like the idea of removing weight from the door and reducing the force on the torsion bars. 

I believe the system was originally marketed by Darryl Tinerstet. He provided the parts needed to convert the solenoid system to actuators. The kit included the actuators, brackets to mount them, the various rods and fasteners, as well as a set of relays needed to reverse the polarity of the power coming from the DLM. The solenoid design uses 3 wires (2 separate internal coils), Lock, Unlock, and ground where the actuators use 2 wires, and the polarity is reversed to change the direction. There is plenty of room for those 2 extra relays, not a big deal for the benefit.

There was also an option to add 2 more actuators in the door so they could be remotely opened. This required that an extra wire be run in to the door to power the new actuator. Some would use a wire that was already up into the roof box (requiring the T-Panel be removed), while others use the now unneeded ground wire for the solenoid. Either way, it was a lot of cut and splice and added 2 more relays.

Then came the remote opener for the bonnet (not sure if Darryl did this or not?), adding yet another relay. And don't forget about having the exterior lights blink when the system is triggers- Yup, another relay!

Darryl sold his business to Toby Peterson who marketed this setup as "Wings-a-loft", and added some other items to the collection. 

Yeah, I could have made it neater,
but way too much stuff in there!

With the rats nest of wires I already had in 6068 to run the VQ35 engine (MegaSquirt), my award winning stereo system, and other electronic stuff- the relay compartment was an embarrassment. Sure, almost no one saw it but I knew it was there.

I wanted to tackle the extra relays needed to reverse the power for the lock actuators. If only the original DLM flipped the relays around, it would have just worked! We were not so lucky, and the board layout made it impractical to modify. I had some discussions with David McKeen, who already offered a number of DeLorean electrical upgrades, if he had any intent on making an updated DLM. He said he had made one for himself but did not see a market for it. 

With that, for some dumb reason, in 2020 I decided to take some of my spare time in quarantine and design my own door lock module. Maybe I could even design the board to incorporate the additional relays needed for the door and bonnet opener and really clean things up! I choose a design based on the use of a 555 timer to generate the needed pulses. It was simple and was going to be so successful I would sell millions of them and retire! Well, with about 6000 DeLoreans left on the road, maybe hundreds. Andrew Zarate would create a 3d file of the plastic box for me (Well, Matt did the printing- I don't have a 3d printer) to print (Thanks again Andrew and Matt!) 

There were a few mistakes, but I was able to get the "Rev A" board to work (more or less). I spent WAY too much time and money on it, and never really got it to work perfectly. By then the company in Houston Texas was starting to sell a digital DLM. While I left the 1st prototype installed in 6068, abandoned the idea of making more. I still have a stack of boards with no parts on them. 

My transistor to activate the marker relay
from the remote control module

I did, however, want to continue to clean up 6068 relay area. Reviewing all of the extra relays needed for the locks, doors, and bonnet, the next relay I chose to eliminate was for the lights. I already had a relay to bypass the failure prone headlight switch (for the marker lights), and thought that there had to be a way to make use of that same relay for the door lock system. The headlight switch energized the positive side of the relay coil, while the remote lock system grounded the relay. I designed a simple transistor circuit to make the relay work either way, and hid it underneath the relays. I also moved the bypass relay from behind the light switch to the relay compartment using the correct Lucas socket, so it slid in with the others.

Relay compartment with the mess gone.

Earlier this year (2022), there seemed to be a flurry of activity around the DLM. The company in Texas was out of stock, and a number of people were looking to install the actuator system without adding all of the extra relays. I had done all the work already and figured why not make a short run of boards to help fill the gap. I had some extra time on my hands anyway. 

Compact DLM replacement

I created a super-small (too small, actually) DLM replacement that had fuse protection for both the circuit and the door locks. It used off the shelf user replicable automotive relays, so if there was ever a problem with them in the future, it would be an easy fix. My relays were configured such that it would work with solenoids or actuators with no extra parts or modifications needed. I place my order for 25 boards, and a bunch of parts, then started talking about it on FaceBook....

Only to find that David had started selling a digital DLM himself, and I had not heard about it. Dave makes great stuff, and I have no desire to compete with him. I assembled 5 of those boards in an effort to sell just enough to cover my initial investment. 2 have been sold, 2 are available, and 1 is 1860. Contact me if you would like one of the remaining modules! 

With the FaceBook discussions surrounding the DLM, there seemed to be a new desire to fix the problem that I was trying to solve in 2020: removing all of the extra relays! Even with the new digital modules being sold that work with solenoids or actuators, it still needed 2 more for the door openers- and that extra wire that has to be run. Gotta be a better way! 

New DLM system, that's a penny!

Again, with some spare time I was looking to occupy with a challenge, I started to design a DLM system that would make the install as clean as possible, My solution is a 2-module system that moves the relays and electronics into the door, eliminating the need for the wires through the body for the actuator/solenoid. That leaves 2 extra wires from the relay/fuse area into each door. One could be used for the signal to open the door, with the relay being in the door itself. The other, I have some ideas for. Constant 12V power could be tapped from the door lights, and the lock/unlock status wires could be tapped right at the switch in the door (still linked between the 2 doors). And hey, while I am at it might as well use that 12V accessory power (for the proposed heated mirror) to disable the door opener when the car is on. It sucks to bump the remote and open the door while the car is going 88MPH down the highway. 

The door lights are protected by fuse 12, which would also protect the new DLM in the door. The accessory feed is protected by fuse 9, so this is significantly more protected than the original DLM. 

As soon as I have time, I will test this new 2-module system in a car, but so far it works perfect on the bench. 

If you are in need of a DLM repair, or replacement - send me a message. I can help you out!