Help.. Pulling my hair out Strange central locking issue

Hi .
I have a 300 TDI disco 1 with an odd electrical gremlin. ( yes what a surprise)
The issue is if I unlock the door with the key ( long story single button fob died ages ago) the central locking usual clicks and all doors unlock. This weak however When you turn the key it blows the Immobilizer fuse. and the central locking does not unlock. The led on the dash is off at this stage and she wont start . If you replace the 15 A fuse she will start and run as long as you dont lock the doors with the central locking..

Im trying to find a wiring diagram for the solenoid. as if that is unplugged in drivers door at least works with the key and no fuses blow but no central locking.

Should there be a permanent live to the solenoid? (i dont seem to have one.)

I have a new solenoid on order to see if its that? any other ideas? im trying to follow the wiring but as its a custom build theirs a lot more than normal in the looms.

Is there a way to test the solenoid?

The door switch seems to be working as i can bell that out and leaving that attached seems to make no difference


Thanks In Advance.

You should pop the other three door cards off and disconnect the door looms and see where you have the dead short as you reconnect them one by one.

15A is actually quite a reasonable amount of amps to blow dead. I think you have a dead short in the wiring and need to find out where.

dieseldog69 said:

You should pop the other three door cards off and disconnect the door looms and see where you have the dead short as you reconnect them one by one.

15A is actually quite a reasonable amount of amps to blow dead. I think you have a dead short in the wiring and need to find out where.

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Ive disconnected the passengers door so far with no change . Should it not take out the door lock fuse not the alarm one?.

Are they all fed from the drivers door or is there a control box hidden someware?

have you opened up the drivers door to see inside there?

You will unlock the door with the barrel but that is also the master switch for the Alarm, Immobiliser and central locking.

Still a dead short so it could be that the main power line to the master lock has shorted out when actuated.

dieseldog69 said:

have you opened up the drivers door to see inside there?

You will unlock the door with the barrel but that is also the master switch for the Alarm, Immobiliser and central locking.

Still a dead short so it could be that the main power line to the master lock has shorted out when actuated.

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Yea had the drivers door apart . With the alarm switch still in place and actuator unplugged no fuse blown .

Ive now got all 4 doors unplugged and the same issue .

Fingers crossed its the actuator . New one on the way.

There's a micro switch on the rear of the drivers door lock barrel this is connected to the security ECU which operates stand alone relay to lock unlock the drivers door actuator, the drivers door actuator also controls the remaining other doors.

U should also see an additional micro switch which is part of the immobiliser function.

discool said:

There's a micro switch on the rear of the drivers door lock barrel this is connected to the security ECU which operates stand alone relay to lock unlock the drivers door actuator, the drivers door actuator also controls the remaining other doors.

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AHH ok
So i can make the assumption if the drivers door actuator is unplugged and the switch in the door seems ok (ie i cat a contact closure on turning the key at the start of the door loom) i should be able to hear a relay somewhere when the key is turned in the door or is it lowenough power it does not need a relay .... Back to under the dash see if i can find the control unit

The central locking stand alone relay is looks large from the picture shown in the Haynes Manual. Haynes doesn't show the position of the relay but I'd expect it to be near the ECU at the side of the glove box.

discool said:

The central locking stand alone relay is looks large from the picture shown in the Haynes Manual. Haynes doesn't show the position of the relay but I'd expect it to be near the ECU at the side of the glove box.

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Thats my next port of call to find that see if manualy firing them i get the same issue. If you could see what specialist vehicles / the bbc did to the glove box ... its better described as a wiring closet