Central Locking nightmare!

[Phil-E30]

Evening everyone,

I have reached a low point in my continued battle with my central locking and could really do with some advice.

My central locking packed in, with the control unit seemingly the problem. I did a repair job on the unit, however, it did not work. I have now purchased a new control unit from BMW but it has not fixed my problem. I currently have four open doors (which I did manually) but my petrol cap and boot are still locked.

Can you experts please direct me to what might be causing the problem, what I need to replace and how I fix my lovely car!

Much appreciated.

[Rav335uk]

Looks like you need to do the Red/Black wire mod.

http://www.e30zone.net/e30zonewiki/inde ... Black_Wire

[Phil-E30]

I have already done that mod, which only adds to the confusion on the persisting issues!

[Rav335uk]

When you did the repair job, did you solder anything?

[Phil-E30]

I soldered the thick red/black wire to the thin red/black wire. Or do you mean anything else?

[Rav335uk]

No, the repair on the unit

[Phil-E30]

The little thermal resistor that goes, I re-resoldered it and it worked for about 12 months. It then went again, I did the repair job again. It worked the first time I used the central locking, however, it did not the second time. I opened up the door and the unit had overheated and melted a bit!

The old unit has been binned, and a new one bought (brand new). However, fitting this new unit has not solved the problem.

[Brianmoooore]

The locking ECU is extremely reliable, and rarely fails, unless it is flooded as a result of blocked sill drains.
The thermal resistor springing open is it doing its job, and not a fault, and as long as it is resoldered without adding new solder, it will be as good as new.
Take the locking ECU out and get the system working reliably with wire links in the plug - one link from brown to white and the other MOMENTARILY blue to red/black to set the locks, then brown to blue and white momentarily to red/black to unlock them. Carefully check that every lock works.
You will probably be doing this with the driver's door open, so move the catch to the closed position, so that the system thinks the door is shut.

[Phil-E30]

Thanks Brian.

Interestingly, there appeared to be absolutely no sign of water or moisture anywhere near the unit. Nonetheless, what drains is it that I should check?

I will give those instructions a go and see how I get on.

[Brianmoooore]

, what drains is it that I should check?

Put a light source on the ground, immediately below where the locking ECU lives, and look in through the speaker hole (with a mirror, if necessary), and you should be able to see two oval slots at the bottom, which are the front drains. There's a third one near the back of the sill.

[ChrisHC]

Do the locks lock and unlock easily if you work them manually with the buttons on the top of the door cards? If they are stiff it may be that the solenoid is straining to move them and that is what melted the thermal resistor. I had something similar and lubricating and adjusting the mechanism had them moving smoothly and eliminated the problem.

[Phil-E30]

The locking ECU is extremely reliable, and rarely fails, unless it is flooded as a result of blocked sill drains.
The thermal resistor springing open is it doing its job, and not a fault, and as long as it is resoldered without adding new solder, it will be as good as new.
Take the locking ECU out and get the system working reliably with wire links in the plug - one link from brown to white and the other MOMENTARILY blue to red/black to set the locks, then brown to blue and white momentarily to red/black to unlock them. Carefully check that every lock works.
You will probably be doing this with the driver's door open, so move the catch to the closed position, so that the system thinks the door is shut.

So, I did this today Brian and it yielded no results, nothing worked.

[Brianmoooore]

Connect a 12 volt bulb of at least 5W, preferably 21W, between the red/black and brown wires of the plug.

[Phil-E30]

Connect a 12 volt bulb of at least 5W, preferably 21W, between the red/black and brown wires of the plug.

Hi Brian, so, I never got round to testing this. Instead an auto-spark I knew came round to have a look. It turns out the actuator on both my petrol cap and my boot are knackered, and this seems to have been preventing the whole system from working correctly. The main thing that worries me here is, what has fried my control unit and these actuators?!

[Brianmoooore]

Usual cause is a flooded locking ECU. Once the actuators are damaged, they will trip the thermal fuse in any replacement ECU.
If damaged actuators are the problem, my first test, with the wire links, should have produced sparks when the second link was connected, even if there was no actuator movement.

[Phil-E30]

My dad did the test you described for me, as I was over in London and the car was back home. Nonetheless, it does seem as though the actuators were the problem. Now I've got an issue with window wipers though!!