My 2006 Expedition cruise control finally went from intermittently working to not working at all. I am looking for a schematic diagram of the cruise control circuit . Thanks in advance for any assistance you can offer !

 

Look no further.

 

The first thing to check is the blue cut out switch on the brake pedal, it's the most common issue. On mine it was not that switch though, I was able to track down a faulty ON switch on the steering wheel with an OBDLink module and Scantool XL with the Ford plugin. You can measure this out without a scantool though, if you don't have one available. My manual has a pinpoint test for troubleshooting an inop cruise control.