Re: [DML] Door Lock Module (long)

["Walter" <Whalt@xxxx>]

John, ahem (big smile)

Awhile back there was a technical discussion on how the door lock module
works. Someone (I don't remember who) drew up a schematic diagram. I went
poking through my door lock module and found a typo in his schematic. I
also wrote up a theory of operation of what every component in the module
does. With a lot of help from other list members and several revisions
along the way, we pretty well said everything that could be said about how
that module works.

Since you recently said some interesting things about these modules, I got
mine out again and looked it over. According to your description, my door
lock module is DHC 110 / 23 409 Iss 4. Thus, my lock module is the latest
known version according to your theory. Considering that my car is an
earlier VIN (03633) and it has the latest version, then in a perfect world
we could guess that only cars earlier than mine might have had the earlier
version lock modules which would be a minority.

But in this world, I'm not so sure that the supposed version numbers that
you see are indeed version numbers. They could mean anything. We could
guess that "Iss" stands for "Issue #". After all, those Irish men who wrote
the service manuals called just about every other part in the car by some
un-American sounding dialect anyway. Even if "Iss 4" is the best version,
it still is a POS for 3 reasons:

1) The first diode is way under-rated and burns up.
2) The relays are way under-rated for the current they are switching. They
can stick closed, burn up solenoids and cause people to get stuck in cars.
3) There is the problem that you mentioned that some of them trip on their
own. Here is my explanation of it: The position indicating switches in the
doors tell the lock module what the door locks are doing. These switches
are SPDT that may not always end up with a solid connection in either throw
position. If the connection is intermittent enough to fluctuate with the
vibration of normal driving, then it causes the lock module to continually
power the solenoids causing them to burn up and possibly trapping someone in
the car.

In order to honestly say that reason #3 is legitimate, I would have to look
over the schematic again, re-read my theory of operation and do some head
scratching. I heard a rumor that this has happened on enough DeLoreans to
warrant designing this fault to be accounted for in the LockZilla module.
If solenoids were burning up but the relays in the OEM modules were fine,
then the problem must have been elsewhere. And that 'elsewhere' was the
lock position switches. I don't know if this has really happened on any
cars.

My advice for everyone on the list: If you still have an original door lock
module in your car, DISCONNECT it. All original modules have unsafe design
flaws. Replacing the weak parts in the module will not keep you safe from
reason #3. But if you are everyone on the list, your eyes probably blurred
over several paragraphs ago and you skipped to the next message by now.

John -- If you want to go in the business of remanufacturing door lock
modules the way you do with fuel senders, radiator fans & such, then resolve
reason #3. If it is not a problem, then run amuck with your rebuilds.
Otherwise you are going to need a new circuit board in that module and the
case probably won't be big enough for it. You will need big relays and a
smarter logic circuit. To make a really successful product, you will need
to make your system upgradeable a la carte to take alarms, keyless remote
entry and door launchers. I already added the keyless remote entry upgrade
to my LockZilla, and I love it. When the door launchers become available,
I'm getting them for sure. If you care, bring some modules to the SEDOC
later this month and we can sit down together and play with them like mad
scientists.

Other DML members have complained that we are trying to re-invent the wheel
by competing with the Zilla product line and that our efforts would be
better spent if we instead put them into fixing unresolved problems
remaining with our cars. If you read my theory of operation about the lock
modules, then you will learn that I am more qualified than most do design &
build a lock module from scratch that would be cheaper and better than the
LockZilla. But instead I dove into totally unfamiliar territory by finding
a way to make convex side mirrors to fix the blind-spot problem on our cars.
I invested the better part of a few days and several hundred dollars, but I
did it! After the SEDOC meeting later this month, the vendors present will
have helped me fine tune and debug this product. Then I will be spending
time I don't have on making these mirrors for them to sell. Maybe it will
be profitable. But one thing is for sure: this is a hobby. It doesn't owe
me any money. If the cars become more cool because of me, then that makes
me more cool, too.

DeLoreans are cool. A DeLorean has me for an owner. That makes me also
cool. May coolness be upon you and your DeLorean.

Coolness,
Walt Tampa, FL