Hasn't worked since I purchased my 2003 Escape XLT.

Pressing ON doesn't light up the indicator. Pressing SET does, but it doesn't hold speed.

Where should I start investigating?

 

My parents have a Ford Edge with a similar steering wheel switch setup and a similar problem.
Theirs started after my mother fumbled a softdrink behind the wheel and the contents leaked into the switches.

You may have a similar issue assuming you bought a used vehicle.

The steering wheel would need to be disassembled and the switches cleaned or replaced.

 

One thought is the clock spring behind the steering wheel assuming the controls are on the steering wheel. Other possibilities are wheel speed sensor, vehicle speed sensor, ABS problems, transmission shift issues and SRS system failures. any of these can and will disable cruise control, ABS, overdrive if equipped, traction control and load sensing SRS if equipped.
Does the CEL, ABS, SRS, traction control lights test on power on and are any of them on in run mode?
A shop with a high end system scanner that reads body modules and PCM may provide more information.

 

Lights are all off except for CEL which only came on recently. (Code P0420 which I have posted in another thread). SRS light was on but I fixed it by fiddling with a connection under the drivers seat. All necessary lights come on when i start the car.

 

Old thread, but as I was fixing other small problems, I decided to try swapping out the Cruise Control Module.

The module has the cord attached to it and cannot be swapped out AFAIK, and the part that attaches to the throttle kept falling off. So I replaced it and voila, I now have Cruise Control.

 

Props for bringing this back with a fix!! Most people would have just let it be and new members would be left wondering if there was any resolve.

Glad you were able to find the issue.