my 1992-240 is unlocking itself.

i locked my car (trunk and doors) at about 7:15am this morning and when i came back at 3:00 pm this afternoon it had unlocked the trunk and the 2 back doors. how does it do that?

 

And is it possible for me to just disable the central locking? It only works half the time anyway

 

sounds like a short or flakey switch in the drivers door.

you could pull fuse 8, but that would also disable the 'courtesy light'

you could pull the two electric lock relays, they are in the central dash, behind the central dash air vents, probably accessible via removing the glovebox (take the passenger side kick panel off first). they are a pair of small cube relays side by side right in the middle of that area. the Overdrive relay is closer to the glovebox, so you'll likely have to move that to get at the lock relays.

there's also a plug in the green wire that runs from fuse 8 to these relays, drawing shows it somewhere around the ignition key? if you unplugged that, it would disable the electric locks entirely.

there's a 3 pin connector just inside of the drivers door hinge, probably near the back of the fuse panel, this has black, green, red wires, if you unplugged this, the drivers door lock + switch would be disconnected, which MIGHT be the cause of your sporadic operation.

inside the drivers door, there's TWO switches, one is connected to the interior lock ****, and the other is connected to the door key, EITHER of these will activate the power locks to go UP or DOWN. the drivers door lock itself is purely mechanical.

oh, the two relays? the one on the left unlocks, the one on the right locks.

 

"there's a 3 pin connector just inside of the drivers door hinge, probably near the back of the fuse panel, this has black, green, red wires, if you unplugged this, the drivers door lock + switch would be disconnected, which MIGHT be the cause of your sporadic operation."


Thank You. This has solved my problem.

 

Amen.

 

so that means the problem is likely in the drivers door, either some flakey insulation intermittently shorting, or one of the two switches (key and lock button) is intermittently triggering on its own.

so... looking at the central locking page of the 1992 240 'greenbook', the green wire goes to the 'lock' side of both switches, and the red wire goes to the 'unlock' side. the black wire is ground.

so for you car to sporadically unlock itself, the red wire is shorting to ground, or one of the two switches unlock side is spontaneously connecting.

me, I think I'd hook it back up, and play around with the driver door lock. work the inside lock up/down/up/down and verify the other doors lock/unlock reliably. do the same with the drivers key lock. remove the inside door panel, inspect what you can of the wiring, check the connections to the two lock switches. the wiring diagram shows another connector 'T' clipped inside the door frame, near the trailing edge and just under the lock switches where the black, red, green wires fork (and the wires from "T" to the key switch are black, yellow, blue instead of black, red, green).

both these switches, the key switch and the lock plunger switch, are momentary contact. the black ground wire goes to the 'throw', and it only contacts the 'pole' when the key is held or the lock plunger is being pushed or pulled.

 

This is an ancient thread, however I just downloaded it for my 1983 245.

I unplugged and plugged the 3 pin connector in the door. It works. Interestingly, I am unable to find the 3 pin connector behind the fuse box. I have a solid wire leaving the connector in the door through the door joint and the 3 wires just disappear into the body of the car beneath the dash.

Thank you again and now I can lock my doors.

George
Arizona

 

Actually I was afraid it was too easy. As I was replacing the door panel I decided to look at the door central losing actuator. All of the wires leading the black plunger (black green and red) have been exposed by the flakey insulation mentioned by Pierce.

I will attempt to splice wires between the plunger and the pin connector. If not successful I guess the hunt will be on for a new part. What a mess.

 

Last note. A replacement plunger switch is only available in junk yards. I initially laughed at the rudimentary nature of the switch setup-and how many cycles this plunger must have endured. It lasted 34 years so not too bad. I cut the three wires, inserted shrink wrap on each wire attached to the plunger and sliced the wires to the plug side.

Perfect action. So if you are having difficulty with the lock-unlocking syndrome, pull the plastic protector from the door which covers the plunger switch. You will find some mischief there due to constantly flexing wires.

Your repair wisdom lives on in the web. Thank you to everyone who contributed to my repair. The car sat for 6 months because I could not lock it. Terrible

 

Now's your chance to revive the central locking. Find a junked car to get an actuator from (any door) and the linkage rod (front passenger door) and add it to your driver's door. Leave the key and lock **** switches disconnected, or repair the disintegrated wires as you prefer. Add a chinabay keyless kit and enjoy central locking from your key fob.

240 Volvo Keyless Entry