I know similar questions have been asked before but I don't seem to have any of the issues previously discussed.

I have a 2005 TD5 SW with OEM central locking and alarm. The 20a fuse blows every time I try to use the central locking. It typically locks then blows immediately on unlocking. I have stripped the doors, degreased and lubricated the locks (which were a bit sticky) and checked the wiring from actuator to door pillar connector. The wiring is all in good condition.

When I put a multi-meter across the orange then pink wires and earth (with the fuse out) I get no resistance. disconnecting each door loom there is resistance on the door loom but none from the door connector. To me this implies a break in the insulation somewhere.

When I find the same wires under the driver's seat there is resistance between the door side of the connector but, no resistance on the side which I believe travels up to the alarm ECU.

I read in the workshop manual 'Each CDL latch motor is connected by two wires to the anti-theft ECU which
alternately supplies power and earth connections to drive each motor to the lock or unlock positions.' I'm guessing power and earth is provided temporarily when the ECU is activated by the fob/key and this is swapped depending if the instruction is lock or unlock.

My question is, should there be resistance between each of these wires coming from the alarm ECU and earth when the system is not powered or activated? Should I be trying to find a break in the insulation or is the alarm ECU fritzed?

Any help would be appreciated...

If you are metering the resistance between the wires that go to the doors then yes, there should be resistance as you should be measuring the solenoid that operates the lock. One of my wires broke where the door hinges and the wires flex in the rubber tube.
This makes sense why your fuse blows on unlock only as the 12v is applied to the wire that is shorted to earth. On lock that wire is getting an earth and it is earthed already.

NeilB said:

If you are metering the resistance between the wires that go to the doors then yes, there should be resistance as you should be measuring the solenoid that operates the lock. One of my wires broke where the door hinges and the wires flex in the rubber tube.
This makes sense why your fuse blows on unlock only as the 12v is applied to the wire that is shorted to earth. On lock that wire is getting an earth and it is earthed already.

Click to expand...

Thanks NeilB.

The situation gets more curious. Assuming that I should only see one or other of the pink or orange wires shorted to earth depending on whether the last instruction was lock or unlock, I took off the instrument panel, disconnected the green plug on the alarm ECU and tested sockets 2 and 3 on the plug tor a short to earth and found they both run to earth.

Assuming again that this implied a break in one of the wires between the AS10 ECU plug and the connector under the seat where these wires (green and purple too) come into the seatbox, I started to try and trace the loom to look for damage.

Having got myself up to the armpits in Waxoyl I couldn't see anything damaged or exposed until I noticed a single yellow wire with a male bullet connector hanging down by the gearbox on the drivers seatbox side. After another 45 mins of grubbing around with a torch, I found a loose female bullet connector coming out of a section of wire protector on top of the main loom where it runs over the gearbox. On the basis of nothing gained, I connected these two, popped in a new fuse and hey presto, locks and alarm are working fine!

I have no idea what the wire does but, it seems to run on its own through a protector up into the bulkhead and into the instrument area. Nor can I explain why it has a bullet connector over the gearbox which looks a bit less than OEM.

At this stage I am so relieved at having apparently solved the problem I can't bring myself to take the instruments off again to find out where it goes. I'll save that for when I install the Mud UK demisters.

I did have my Landrover specialist install an overdrive unit and I guess they may have either cut and spliced the wire or, if its OEM to have a connector there, may not have reconnected it properly but, who knows...

Anyway, if all else looks good, check for a loose yellow wire by the main loom next to the gearbox.