I know this sounds demeaning, but it happened to me: Have you checked to make sure that your cable didn't break? Mine broke twice in a few months, from being moved around and getting kinked. I should have made a new one from a length of bicycle cable, but I bought a new Volvo one instead for about $30.

If it's not that, I second the theory about the dash-panel wire. On my 245 it was quick to come off, and if you were reaching around up in there you might have pulled it off accidentally. Another thing; is the unit mounted level? Mine wouldn't work unless it was. I'm guessing that there's a mercury switch inside the black box.

Good hunting...

Since it was self-inflicted (happened while you were messing around with something else), anything that might commonly happen to a similar car doesn't apply to yours...but I'm going to take a stab at this anyway.

Did you pull the guage cluster when you were working on it? The speed signal to the cruise controller is a single yellow push-on wire that goes onto the "E" connector behind the speedometer. Wrong terminal or not connected will certainly kill the cruise control.

Another thing you may have done is mislocate the silencer pad (underdash cover) causing the brake pedal to be held down slightly (it only takes 1/4") which can keep the vacuum "dump" valve open. It's easiest way to check this by simply lifting the pedal with your left foot and holding it up while you try the cruise control. If it suddenly works, you have a pedal/safety switch adjustment or binding problem.

Without a wiring diagram you will need s@#t luck. There are a number of plugs from the stalk & control unit that get plugged into the harness at various locations inside the dash. Apparently one of them may be dislocated.

I wish you good luck and a good thanksgiving.