If neither the key nor the pull-up knob operates the central locking - in either direction - the only thing I can think of that is common to all, is the ground wire. Possibly this has become separated at a connector, or broken apart, maybe where it is flexed in the rubber boot between door and car body near the hinges. You'll have to remove the inner door panel to inspect.

If a lock/unlock solenoid has been installed in the driver's door, the drag created by this definitely makes the key harder to turn, but I've lived with this for years now.

There are a number of aftermarket keyless entry systems available which have driver's door priority unlocking, and which can be adapted to the 240 central locking system. You need to install a lock/unlock solenoid in the driver's door (which it sounds like you already have), and connect the "unlock" wire of this to an additional SPDT relay which is triggered by the driver's-door-only pulse from the keyless module. The "lock" wire of the solenoid can be spliced into the other doors' lock wiring - which is Yellow in my 1983 wiring diagram. That way, everything locks at once.

Incorporating remote trunk unlocking is relatively simple on the earlier 240's like our 83, so Art Benstein's comment can be your guide on your 1990.


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Bob (son's 81-244GL B21F-M46, dtr's 94-940 B230FD, my 83-244DL B23F-M46, 89-745(LT1 V8), 98-S90, 77MGB and four old motorcycles)