1987 740 gle--central door lock mechanism does not work.Started in cold wet weather. Haev to try many times with key for success; same with inside--pull / push driver button many times. gave up at this point. Any solutions???

 

Not sure exactly what your issue is but I would subject posting this in the RWD 740 section.

 

Hi, I am experiencing the ¿same? problem: drivers door key locking mechanism work fine, however the three passenger door locks works only properly when "unlocking" the driver's door with the key !
Any suggestion ? An 86 years old Volvo fan with a 28 years old 740 almost as new condition.

 

I'd probably arm myself with the greenbook wiring diagram for your year/model, and a volt/ohm meter, and start checking voltages and stuff while manually exercising the lock... there's a central locking relay which gets involved.


here's the wiring diagram for 1992 740/940 central locks... afaik, they all are pretty much the same.



so, the drivers door lock **** has a switch (3/14), this indicates the lock is going up or down, it goes to the relay 2/7, whihc powers the solenoids at the other locks and tells them to also lock or unlock, this switch is wired to a relay in the central console (forward of the ashtray), and that relay runs the lock solenoids on the other 3 doors, and the trunk. its not a simple relay, it has a little circuit board inside with some electronics, and two relays, one for lock, one for unlock.

looking at this diagram, I see 3 possible failure modes... 1) the switch on the drivers door lock plunger is messed up. 2) the relay is messed up. 3) the wiring to/from the drivers door is messed up. if your car is a 1987, it may be subject to the 'biodegradable wiring' that plagued volvos from 1982 to 1987.

if you pull that relay (on the 92, its the middle one on the row closest to the fuses, behind the ashtray), and probe the pins, pin 4 should be grounded when you unlock, and pin 9 should be grounded when you lock. If this test fails, its the switch or the driver door wiring.

if you jumper pin 2 to 3, and momentarily jumper pin 1 to 5, the locks should unlock. if you jumper pin 2 to 5 and momentarily jumper 1 to 3, they should lock. if all those tests pass, odds are its the relay.

 

First check the relay, marked K. Then I'd check the main lock actuator in the driver's door. 99% chance the trouble is there.

 

Hello,

I wish to thank, all of you, for your kind help. I will try all suggestions and will let you know the result.
Regards, Etienne