Trunk lock problem

[Helloball]

God only knows what the problem is with my trunk lock.? It doesn’t lock when deadlock with key in the drivers door. When I use key to deadlock the trunk it doesn’t lock any of the doors either. So electrical nightmare is causing this not to happen?

[dannyzabolotny]

It's usually one of two things— the lock actuator in the trunk is faulty, or more likely, the wires going to the trunk are damaged and not sending the signals to lock/unlock the trunk. The wiring that goes into the trunk runs along the driver's side trunk hinge, you can unclip the plastic cover (if it has it) and check the wiring. I've had to repair the trunk wiring in quite a few E34's.

[shogun]

broken trunk wire loom https://www.bimmerforums.com/forum/s...-wiring-issues There are Trunk Repair Harness kits - Left - E34 available
https://www.bimmerforums.com/forum/s...ss-Replacement

[Helloball]

Will i just need the left side part number and maybe defogger since I have the US spec 525i sedan? There is only wiring on the left hinge of the trunk lid.

[dannyzabolotny]

The sedan wiring is much simpler, I would just look at the loom on the left hinge and check for breaks in the wires. It can be fixed easily by splicing in new wire with crimps/solder/whatever method you prefer. That's what I've always done, it costs almost nothing.

[E34 Lives]

If your entire locking system is not working then you need to check the fuse and make sure it is not blown. The old BMW uses a thin wire fuse and sometime there might be a hair line break but only visible in bright light. Happen to me on a fuel pump fuse, only holding it up to bright sun light did I see the hairline break that was after I replace my fuel pump. 🤣

Once you get locks responding, then you might need to turn key to open and close a few time to sync them up.

I have replaced trunk lock actuator, they do go bad over time. It is very straight forward.

It is also not the end of the world with trunk lock not working as there is no trunk release in passenger compartment and rarely does anyone go around pressing the trunk release button on locked cars, for time being just don’t put anything too valuable in the trunk.

After verifying the fuses are good, checking the loom wiring on the trunk hinge (US driver side) should be your next step. You had tail light and license plate light problems a while back and should have went through each wire to look for breaks. Remove the wrap and go through each wire, to check.