central locking opens after locking

[grasshopper2]

I got a 1987 730i se auto, great motor, central locking functions but when I lock it, it opens immediately automatically, I have to lock it again for the doors to remain locked. Why does it open again? can anyone advise how to rectify the irritation?

[Flywheel]

Originally Posted by grasshopper2

I got a 1987 730i se auto, great motor, central locking functions but when I lock it, it opens immediately automatically, I have to lock it again for the doors to remain locked. Why does it open again? can anyone advise how to rectify the irritation?

I have exactly the same problem and know why, so maybe this will help. On my car, a previous owner removed, for whatever reason, the solenoid on the boot lid, effectively removing it from the central locking circuit. This means that the boot has to be opened and locked manually, using the key. The side effect is that when I lock using either the key or the remote, the locks all pop open again,meaning I have to re-lock again,so, I'd check that all solenoids etc, on each door are fully operational, with good connections. I'd check the boot first, as this is the most accessible, and most easily disturbed. The doors will have to have the inner door cards removed to investigate further. I dont imagine its a fuse, as the locks actually operate, which they shouldnt, if this was the case. A bad connection or contact is your most likely cause. Hope this helps.

[grasshopper2]

Thanks for the info. I checked all the solonoids and they are all fine. Someone told me to check the master control unit, but whete or what is that?

[Flywheel]

The only item that I know of that might be the "master control unit" that you mention, is the General Module or ZKE module as it is often known.
This is located in the rear power distribution/fuse box, under the back seat by the battery. The back seat just pulls straight up with a sharp tug, pulling upwards on either side of the transmission tunnel. Some seats apparently are bolted down, so no harm to check first! The ZKE module is one of two similiar ( long rectangular) units in the power box. Both are located about the centre of the box, with the ZKE below the other one. Either way it should be marked. Otherwise you only have fuses and relays.Fuse number 20 @ 7.5 amps located in the front power distribution box is responsible for central locking. Might also be worth a look. Hope this helps.