E30 central locking issues

Everybody who have a BMW E30 knows that it's a miracle to have a fully working central locking.
But the most of us dont have it fully working, or not working at all.
I will describe the most common issues of the central locking and how to fix them, as i build a fully functional central locking from the ashes.

First of all, i want to describe you the parts of the central locking system and what is the purpose of each one of them.

Introduction


1. CLCU (Central locking control unit)

This is the "brain" of the central locking system. It is located behind the kick panel on the drivers side of the car (depends on the country).
It is mounted on a metal plate that holds it still to the chassis as inside the CU there is a system that controls the central locking in case of crash (it automatically unlocks the whole car in case of impact). Thats the reason that the CU must remain tight at its specific place.

2. Central locking actuators

This is the central locking actuator (this makes the door lock/unlock)
As you can see it has 2 colors.
The coupes have 4 actuators (2 at doors, 1 at trunk lock and 1 at gas tank door) and the sedans and tourings have 6 actuators (4 at doors etc.)
The colors of the actuators are the following:
Drivers door - White/Red
Passenger door - Red/Red
Rear doors - Red/White
Trunk and gas tank door - White/Red.

3. Central locking microswitch

This is the so called lock microswich. It's held by a metal bracket in the passenger door near the door lock cylinder. The lock cylinder has an "arm" that in the position of locking pushes the microswich button and tells the CLCU to lock the car. Thats why the CL is sometimes only unlocking the doors via the passengers door but not locking it.


Troubleshooting:


1. The famous "drivers door loop".

These are two Red/Black wires coming from the main harness, going through the pin connector at the drivers side door, making a loop inside the door and getting back in the CLCU.
Tha main known issue with those wires is that they corrode in time inside the door and don't make the proper connection.

This is pretty much the explanation of the process. You must locate the two Red/Black wires in the kick panel area and solder them together to bypass the loop in the door. This is one of the reasons that the central locking isn't working.


2. Pin connectors rust/corrosion.

Another reason of non functional central locking is corrosion on the pins in the doors connectors.

Disassemble the connector, spray with WD-40 any rust or corrosion spotted, check the pins&wires and assemble back together. It's easier first to put the rubber boot on the female connector before connecting it to the male part.


3. Door lock actuators.

This is common issue, leading to non-working CL on specific door. The most common problem is that the selenoid inside the actuator isn't working at all and can't move - can't lock/unlock the door.
Each actuator is located inside the door, held by 2 screws.
Dissasemble the door card (Article: Removal / Assembly of door cards.) and locate the 2 screws holding the actuator in place.
Inspect for wire damage at the connector and make sure they are adjusted properly.
The adjustment is pretty easy: untighten a little bit (move the actuator freely), push the door lock stick inside (locked position) and do the same with the actuator (locked position) then adjust the actuator down as much as there is no free movement of the actuators arm (if you pull out the door lock stick it must immediately pull the actuators arm with no free movement before it pulls the actuators arm out). Then tighten back the screws and you are ready. Inadjusted actuators could be a problem in the central locking system too.


4. The microswitch.

This is very common problem with the passengers door.
The microswitch is held by a metal bracket near to the door lock cylinder. The door lock cylinder has an arm that pushes the microswitch button and sends a lock signal to the CLCU.

The most common issue is that the arm on the cylinder is wore out and can't push properly the microswitch. The best solution is to buy a door lock cylinder rebuild kit (OEM part ~ 50$)
.If you don't want to do it, the other way to fix this is to figure out on your own how to make the wore out arm push the microswitch properly. Feel free to experiment. I did it myself with building a custom metal arm (thats sits on top of the microswitch)

5. CLCU Internal fuse.

The CLCU has internal fuse that desolders itself in case of problem with the CLCU (as if there is a problem the CLCU get hotter) or can just break.
You just need to dissasemble the CLCU , locate the fuse and solder it back together.

This is it pretty much everything folks. A problem with the central locking can be damaged wires etc. but i assume you can figure that out by yourself.
Feel free to ask if you have an issue outside the mentioned in this article.

Best wishes,
Petromir (E30 Touring owner)

Photos: Google, E30Tech.com