I just replaced both sides of these harnesses on my wife's 88 last month.

New wiring runs about $18 a side from FCP Groton. Dealer gets twice that, so it's a good deal. The harnesses are basically all made up, with all the right connectors and wire colors.

Once you receive the new harnesses you'll notice that some of the connections are not inserted or have no end on them. Don't install them until the wires are fed thru the tailgate.

You will want to have about a 4 to 6 foot long piece of flexible but strong wire or heavy string. You will want to tape and tie this to the wire bundle as you pull them through, and then attach the new wires to this and pull them back through the tailgate on the sides of the window.

You'll need to have an assortment of tiny jewelers screwdrivers or equivalent, to release a couple of contacts from their insulating terminal plugs.

Each wire ends in some kind of a plug or socket that goes to a unique connector on each item in the tailgate. You've got power to the power lock, defrost, 3rd brake light, license lights, and rear wiper back there- stuff from a lot of different circuits.

Up in the rear headliner, there's a round plug on each side. You pull the headliner folded edge out of the steel lip around the hatch- just stretch it towards you and the plastic edge flips right out of the lip. Once this access flap is hanging down, you can get at the hinge bolts and the plug in each corner. The hinge bolts are 12mm or 13mm, I don't remember which.

The hinge has to be removed to do this. You only take off one hinge at a time, and you need a friend to help support it. You can take off the hatch support gas strut- in fact you probably want to. Use a rag or towel to keep the center of the hatch from scraping the body.
There are screws at all sorts of weird angles that hold each hinge on. Figure out how you're going to remove each one, and leave the easy ones for last- you don't want to be fiddling with the last one in a difficult spot to access, with the hatch falling on your head.

The hinge has to be removed from both sides, then the old harness pulled through the roof, and the new harness fed through the hatch, with the round end stuffed through the roof hole. Then the hinge goes back down over the new harness. It lays into the groove in the hinge quite tightly.

SOme of the wire ends need to be separated or cut from the old harness to feed through. Save every connector and clip- there are one or two you have to recycle. Each wire releases by depressing a tiny finger on the metal terminal in one way or another, some more creative than others. You'll see what you have to do when you have the pieces in your hand.

Good luck with it and enjoy the black sealing goo under the hinges! Just checked FCP's page, and the harness is $13 a side, so it's even cheaper than I thought. Not a terrible job, you can do it all in a single afternoon. See how one side goes- you can do it in halves.
Parts are listed toward the bottom on this page:

http://www.fcpgroton.com/volvo240other.htm
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Rob Bareiss, New London CT ::: 87 244DL- 249K, 88 245DL- 181K, 84 242DL, 89 244DL parts, SOLD: 86 244, 88 244GL, 87 244, 91 244, 82 245T, 88 744GLE, 86 244