I just wanted to share my discovery. I have a 2004 Lightning (150 Heritage), left over 2003. The Cruise Light would flash when activated but not come on. Then it wouldn't even attempt. I tried the self test, but it would never complete the sequence at the RSM step. Found a YouTube video, "#1 Reason Your Ford Cruise Doesn't Work Anymore" video. 90% of the time it's the Cruise deactivator switch, which is redundant. Evidently to activate the cruise the "deactivator switch" aka "cruise control release switch" and the brake pedal switch must both be closed to work. The cruise control release switch fails in the open position. You can test continuity of the switches for failure. I simply put a jumper wire on the release switch plug and my cruise worked! Ordered the switch from Rock Auto $18.02 + ship for the Motorcraft version. This switch can be found mounted on top of the master cylinder on most models, excluding Windstar and Super Duty.