I posted this same problem a few weeks ago with a 1992 f 250 diesel, and since then i have done some messin' around under the hood. The problem is that the cruise control just will not come on. I press the "on" button and then press "set accel" and it just dont work. I checked the fuse. still good. I tested the voltage to the actuater device by the brake master cylinder. There is juice there. The ground is good. The vacuum lines appear to be in good shape. I was thinking maybe get a vaccum gauge and test for vaccum. Could it be the switch on the steering wheel?