Glad you found it. Art correctly surmised it was very likely a broken black ground wire through the hinge once you confirmed the RF door switch was also not working and the relay was seemingly okay.

As for a repair, a butt joint sleeve crimp will quickly get you going again, but if you want it to last longer then you need to keep any splicing out of the hinge flexing area either by pulling in a bit of fresh wire if there's enough slack or by adding a short section of new wire.

As I mentioned in my FAQ comments, I'm quite impressed with the innovative design of the power window switching circuitry. No high tech logic circuitry involved, it's all done using flip/flop motor polarity with daisy chained momentary DPDT switches for local/remote control. It would be interesting to know if this design came out of North America or Europe -I'm guessing Detroit.

There were two main weak points in Volvo's implementation of this design. One is using switches mounted face up that can too easily collect dirt down in the contact area. The other is using standard automotive stranded wire at the door hinge areas that was not up to the job of all the flexing it would have to undergo over the years, same problem as with 140/240 tailgate wiring. Copper of course hardens and gets brittle the more it is flexed (as well as when heat cycled). One way to help reduce this is to use a wire with lots of fine strands (with reinforced braiding for added support) -think DVM test lead wire vs. single strand solid copper wire. Another is to spread out the bending, first by making it a longer smoother arc, and second to replace some of the bending with a bit of twisting, hence the Z-routing of wires in a tube with the later 740/940 tailgates.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now