Locks

How do you ensure the general riff-raff know that the E30 is an exclusive vehicle, only for the privileged? By locking them out, of course. Locks are also useful in preventing people stealing your ICE and Murray Mints.

Overview

Each E30 is fitted with a number of mechanical locks to secure the front doors and boot or tailgate. But the whole lock set will also include the ignition barrel, the glove box and the petrol cap, making six locks in all.

These locks are specific to the car; in the event of you losing your key, BMW can issue a replacement key if you provide them with your VIN number. It is also possible to "recode" door and glovebox locks by disassembling them and replacing their internal tumblers with a kit available from BMW. However, it is impossible to recode your ignition, boot or petrol cap locks. Learn more about recoding door locks.

Central Locking was a popular optional extra; so popular that it's very uncommon to find an E30 without it.

Components

Door Locks

The front doors of each E30 carry two mechanical locking barrels. When operated by a key, these barrels will rotate, operating the locking catch via an arm on the back of the barrel.

It is possible to dismantle a door lock barrel and recode it to fit a different key. Learn more about recoding door locks.

Boot

The rear end of each E30 is secured with a boot lock that locks the boot lid. Touring models also have a rear lock for the tailgate which is specific to that model.

While the boot lock is easily removed by unbolting it from the inside, like the ignition barrel, it is a sealed unit that cannot be dismantled and recoded. If your boot lock is broken, you will need to order a specially recoded one from BMW to match your other keys.

Ignition Barrel

Mounted on the steering column, the ignition barrel connects directly to the ignition switch and also controls the steering wheel lock. It is a self-contained tumbler unit, and slots neatly into its aluminium housing. It can be removed and replaced, but you will need the key to do so. Learn more about replacing the ignition barrel.

Glove Box

The glove box is a simple tumbler barrel system. When locked, the tumbler rotates to disengage the lever arm within the glove box handle, preventing the glove box from being opened. The barrel itself is easily removed from the handle by means of a circlip, and it can then be disassembled and recoded to a new key if required. Because of its size, the glove box lock only has 7 lock tumblers instead of the other locks' eleven.

Petrol Cap

The petrol cap is a standard unit on all E30s, and is manually locked or unlocked with a key. This lock is specific to each vehicle; you can't disassemble the petrol cap lock, so if you lose your key you're going to have to break the cap to open it.

Don't confuse the petrol cap with the petrol flap, which is controlled by the central locking.

Central Locking

One of the luxuries we take for granted with modern cars is not having to pull up the little plastic knob to unlock a door from the inside. E30s were no different, with central locking being a popular optional extra. Putting the key into either the driver, passenger or boot lock and unlocking should unlock all the other doors at the same time.

This is done with microswitches; little contacts that are closed when the lock barrel is turned. This sends a signal to the Central Locking module to power the actuators, which are little more than electric arms that push or pull that plastic knob up or down.

The central locking system also controls the petrol flap. If your locking system has failed, you can still unlock the flap manually from inside the boot.

Microswitches

The microswitches are exactly that; very small switches which are opened or closed depending on the position of the door locks. Each door lock barrel is shaped with a small lump of metal. As the barrel spins with the turning of the key, this lump will rock over a metal spring that will switch the central locking on or off.

Each microswitch is mounted to a solid metal plate that slots around the door lock inside the door skin. It is held in place with the same C-clamp that holds in the door lock.

Actuators

Lock actuators are simple electro-mechanical solenoids. Receiving power from the central locking relay, they will pull or push on the metal rods inside each door that work the door lock.

In the event of a burned out or broken actuator, that door will be locked solid; you will not be able to work the lock by hand or key. The solution is to remove the door card (which often means removing the seat on that side first), and then unscrewing the two bolts that hold the actuator in place. With the actuator loose, the door can be unlocked by hand and opened.

Central Locking Relay

The central locking relay is the clumsy brain of the central locking system. Constantly powered, it interprets signals from the door microswitches to power the actuators into their locked or unlocked position.

Because of the location of the solenoid above a prime Rust location at the base of the A-pillar, the relay is prone to water damage, which will kill it. In that event, the only solution is to replace it. Learn more about central locking relay problems.

Wiring

All of the central locking wiring leads to the central locking relay. From the relay plug it's possible to test the workings of the system, wire in a new relay or install an aftermarket system.

The relay receives its lock and unlock signals from the microswitches. There are lock request inputs (Yellow/blue and green/black), and two unlock request inputs (green/blue and yellow black). The yellow/blue lock request and green/blue unlock request is used by both front doors, and the boot and rear doors use the others.

The yellow/blue at the lock motor is the lock request wire, and the request is sent to the relay by earthing it. On all the lock request switches on the car, except for the driver's door lock motor, this connection is straight to earth, but on the driver's door lock motor, the yellow/blue is connected by blocking diodes to both the blue and the white wires which power the lock motors themselves. Both these wires are earthed by the relays in the central locking relay when it is at rest.

Petrol Flap

The petrol flap is a simple metal door that unlocks when required via the central locking. There is no manual release lever like on more modern cars.

The only problem people report is when the central locking stops working, you can't access the petrol cap. To bypass this, open the boot and look for a flap cut into the carpet lining on the right hand side. Peel this back, and you should have access to the petrol flap actuator and control rod; these can be operated by hand to open the petrol flap.

Common Problems

Central Locking Not Working

The central locking system fitted to E30s is a relatively simple design, but decades of wear and tear takes its toll on the switches and actuators eventually. Couple that with corrosion of the wires and the occasional flooded relay, and the system becomes open to a whole host of issues. To get them dealt with, learn more about central locking problems.

Door Won't Unlock

This is a common problem with a burned-out or deadlocked actuator.

What can happen is the actuator seizes up, which in turn will make the door impossible to unlock. This may be caused by the central locking system getting damp and sending a deadlock signal to that actuator only, or it could just have died, but either way I'd expect that to be the source of your problems.

To sort it out you need to get the door card off, and that's quite tricky to do without being able to open the door. Some will recommend removing the seat on that side so that you've got more work space, but here's how to get the cards off.

With that off, you should be able to see the two hex screws that hold the actuator in place (bottom corner closest to the B-pillar). Just undo those, and you should be able to lift up the pin to unlock the door, so that you can then explore inside the door and retrieve the actuator.

While removal and replacement of the actuator is relatively easy, further investigation will be needed as to why the actuator failed in the first place.