E30 Zone

I hear the central locking is prone to failing on the E30, which mine has done.

What are the common causes? Easy fix?

Cheers in advance

http://www.e30zone.net/modules.php?name ... ocking.htm

There's a brief mention on there of the pins in the door connectors - the red / black wire in particular causes problems. It carries power into the connector, into the door, back out again and into the relay.
A recommended mod is to disconnect both red / black wires from the connector and connect directly.

Being in the bottom of the A pillar, the relay can also get water logged. When this happens the unit has a habit of killing the door solenoids, though I've not heard of many cases of this.