From digest.v7.n244 Tue Sep 23 12:37:17 1997
From: Jim Cash <j.cash_at_sympatico.ca>
Date: Tue, 09 Sep 1997 08:00:37 -0400
Subject: Re: Re Central; Locking - E28
Just some additional information - so as not to mislead you.
I can't remember which year you had, but I know it was not an 82. My
drawings are for 82, and while I think they will be the same, they might
I saw a note from another person to you mentioning the key lock unit
I do not think it has electrical connections, but then I am working from
knowledge about an 82. I also gave you some contact information about
the actuators - I kept this simple but the following is more precise.
Here is how the 82, and I assume your, system functions.
The key locks are mechanical and are independent of the electric locks.
But they are physically linked at each door and the trunk so that the
actual lock mechanism is controlled by the combination of the key &
electrical actuator linked together. When you turn a key you are not
only locking/unlocking that door physically, but also moving the
actuator for that door - which then sends a lock/unlock "request" to the
control unit. The control unit then sends the appropriate lock/unlock
"signal" to all the actuators (in parallel), which use a solenoid to
produce the same movement in the locking mechanism as does the physical
Each actuator is actually a double unit.
When all actuators are in the same position (locked or unlocked) the
system is at rest. As soon as one actuator is moved (i.e. moving the
solenoid from unlocked to locked position) now a ground appears on the
lock request lead to the control unit - which reacts and sends a "lock
signal" to all actuators. If they all respond and go to their locked
position, then their associated request switches are now grounding their
"lock request" leads. Since the system is already locked, and since
there are no grounds on the unlock leads - all's well.
But if one of the actuators fails to operate, or if one of the internal
switches has failed then you immediately get a ground on the opposite
lead. Depending on the nature of the fault it might affect only the
locking, or the unlocking operation.(i.e. a switch shorted in the unlock
position will allow all the locks to unlock, but will not allow them to
lock.) If this is intermittent due to a slow acting actuator, or
corrosion in the switch, then you will get both situations, at times.
The contacts on each door actuator are as follows:
- - solenoid motor - lock signal from control unit - contact #1 - blue
- - solenoid motor - unlock " " " " - " #2 - white
- - request switch - lock request - sends ground to control contact #7
- - request switch - unlock " " " " " " " #6
- - shown "unused" on mine but I think it goes to alarm circuit.
- - request switch - ground connection.
The trunk is the same except that the function of contacts 3 & 4 are
reversed (this might be a typo).
Also the wires and connections at the control unit are different as
3. - request switch - unlock request - ground to control contact #9 -
4. - request switch - lock " " " " " " #8 -
The drawing shows the lock request leads from the doors, and the trunk
then connecting together in the control unit. While this makes sense
functionally it does not account for why you can sometimes use the trunk
unit when the doors will not work. I suspect that the drawings not
completely accurate inside the control unit.
The control unit also has and internal "automatic unlock" switch that
initiates an unlock request should it sense an "impact" greater than 5
g. This is what unlock your doors in an accident. I remember hearing
that it also reacts to a roll over - never tried it. That switch is
powered in "Run" and "Start" positions on contact #5. It is not powered
when car is off so that you can not unlock a car by running into its
bumper (impact) - yes some of the older ones work this way.
In case you are interested, I found it very useful to have a toggle
switch on the console (just below and to the right of the shifter) to
operate the locks. I just drilled through the little plate to the right
of the automatic shift - it pops out) and mounted a double throw toggle
switch. I connected the centre pole to ground and the other 2 leads were
connected to the lock & unlock request leads that go to the control
unit. You can splice into them up under the dash a various places - or
you can go right to the control unit.
Suggest you mount the switch so that pulling it back causes a lock
request. That way you can get in the habit of locking the car as you
shift into gear, and unlocking as you shift to Park.
Hope this, and previous info helps you find your problem.
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