Don't group too many things in at one time. Best idea is to follow one problem and then the next. Meaning the clock could be just old capacitors and may or may not be part of the puzzle. Same with the guages and lights. That is a voltage issue in the Cluster and most likley not part of the Locking system. But I have been wrong many times before.

Start with the door relays. Relays on Volvos are now very old and can cause you all sorts of grief. Had an overdrive relay that would sing like a seat belt buzzer every so often before it just quit. Fuel Pump Relays are the stuff of legend of course (have two extra right now, just in case). With that said the door lock ciruit has two (Locking and Unlocking). This may just be an intermittent unlocking relay. Fuse 8 in the fuse that sends voltage to both relays, so you are on the right track. Try replacing them one by one and checking then checking connections and grounds. They are in behind the center console and the center vents. The ground in the group at the top right side of the center cluster when it is opened up. You may be able to reach the relays by taking out the glove box. The first one you come too is the Overdrive relay and the Door lock and unlock relays are next up in that tunnel behind the vent and dash. There is also a blue connector on the drivers side behind the center console that may be loose, and you can also disconnect the relays by seperating that connector. You can also check from shorts in the wiring there also.

The best course may be hit the PUP and get a couple of relays. Try the left hand relay first that is the unlocking one. At least before tearing into a door it seems like the place to start.

Good Luck,

PT