Red/black wire mod

[Steve007]

My brother in law has just picked up a 89/90 320 cab. It has a few problems one being that the boot lock only opens all doors. Reading on here seems that this is a common fault with the central locking.

After reading here I will perform the red/black wire mod. I'm not too clear where I'm connecting the wires though from the wiki.

Am I right in thinking that I need to connect the three wires together on the car side of the white plug and not the door side?

Watch this space for more questions such as "how the f**k did this get an MOT with the power steering pissing out its fluid?"

[Speedtouch]

Yes, you remove the speaker in the driver's side A-post and reach in to connect the wires.

No need to touch the wiring inside the door itself.

[Brianmoooore]

"how the f**k did this get an MOT with the power steering pissing out its fluid?"

By emptying the rubber boots and wiping up the mess just before submitting it for its test, and making sure you don't use full lock in the meantime.
Wiring mod. is as speedtouch says - don't mistake the red/brown for one of the three red/blacks. this mod. should be done as a matter of course for non locking related reasons, but I don't think this will help with your problem.
Are you saying that turning the key in the boot unlocks the doors (it should), but leaves the boot still locked?

[Steve007]

No I think the boot lock operates all doors but the door locks only unlock themselves if that makes sense. But I have not troubleshot the system yet.

Seems the solenoid works but the switch does not?

[Brianmoooore]

If the car has been locked by the boot, and the key turned to the dead lock position, then the boot shouldn't unlock from the doors.
I'm not convinced there's anything wrong yet. Do a bit of further investigation and report back exactly what does or does not happen.