OK, I have an 83-84 Limited 4.2 auto with cruise control (that doesn't work). I've slowly been fixing all the little things, but having the cruise working is the next project. I have an aftermarket manual, but I might as well read a McDonalds menu, for all the useful info it contains about diagnosing the cruise control system. How, and where, do I start?
The cruise control on my wife's 95 Lincoln quite working and it was just the fuse. I don't know if yours is a simple fix as that but never the less its a good place to start.
Check the fuse. Sounds elementary, but check the fuse 20. It controls the radio and cig. lighter. Replace it either way.
Make sure the vacuum hose is hooked up to the brakepedal. Sometimes people change the stoplight switch and go for the cheaper one that doesn't have the cutoff switch included. It's job is to release the cruise if you hit the brakes and the stoplight fuse is blown. I had one someone stuck a golf tee into so it was plugged. Hit the cruise control and the car accelerated to 70 mph before I turned the cruise off (with my foot on the brake the whole time!)