A year ago, the central locking in my wife's '90 740 wagon stopped working entirely. All locks must be locked or unlocked manually.

I have determined the following:

1. There is power getting to the driver's side door switch (I disconnected the in-line connector and test with a voltmeter).

2. The inside of the central locking relay (# "K") appears okay (no broken solder joints/I sparyed it with contact cleaner).

3. If I jump the wires that run to/from the driver's door swith, I can feel and hear a slight click at the central lock relay.

4. There is power getting to the passenger side door lock mechanism (I disconnected the in-line plug, inserted a voltmeter, and had my seven year old daughter unlock and lock the driver's door). I seemed to be getting around nine or ten volts or so.

5. I love the car but hate Volvo interior plastics (but that I knew already).

My questions:

1. If the passenger door is getting power, does it mean that the drivers switch and relay are okay?

2. Might it mean that the passenger door actuator (or whatever it is called) is dead?

3. If the passenger door actuator is dead, would that prevent the rear doors from working?

One more possible clue. At the time that this died (again, at least a year ago), I had some reason to suspect that the actuator at the tailgate was screwed up. I can't remeber now why I thought that, but I think it might be that the tailgate latch was physically stuck. I took the cover off, and disconnected the linkage to the power actuator. The lock then worked fine, manually (though I may have sprayed it with silicone). The power actuator seemed impossibly hard to work by hand, but then again, maybe that's how they are supposed to feel. I left it disconnected so we could use the tailgate via key. All other power locks remained dead. At that point, I started wondering if the central lock relay got fried by the tailgate lock being stuck. Now though, as I said, I do have power to the passenger door, so my guess is that the relay is okay.

Please, almighty smart ones, help me figure this out!!! My wife has been a champ about this, but with kids, the dead powerlocks are really a pain in the neck!

Thanks,
mrad