Were do I start to trouble shoot cruise control that's not working

W/o year--make--model, I can't help. My database only covers vehicles sold in the US.
Maybe your fuse box or owners manual will tell you which fuse is which?
Any applicable trouble codes?

The rear window defroster can be tested by checking for power out of the fuse box to the switch which operates a relay usually 4 pin 2 pins are the controlling side and the other 2 are battery power and the window element wire. Some switches have a led light in them that shows power is completed thru the switch . With a volt meter test wires at rear window some times if to many breaks in the grid stops the system from working. the cruise control has a servo with it's own throttle cable check for broken cable and check for engine vacuum to servo. then test switches on steering column with a ohm meter for proper continuity and test brake light switch.

U need a new dealer. What is he there for? Aren't they supposed to be the experts on your car? If your cruise control does not work properly doesn't it make sense to trouble shoot or replace the module that controls that aspect of your car?

get a factory manual, FSM.
or login to alldata dot com
or mitchels. online.
3 ways to trouble shoot complex functions an any car.

You can not do much without wiring diagrams

Where would you start your testing?

You don't even know what is in the system

Need factory wiring diagrams or print what you
need at a local repair shop from their data base

CRUISE CONTROL PROBLEMS CAN BE CAUSED BY FUSE OR FAULTY BRAKE LIGHT SWITCH OR BLOWED FUSE TO BRAKE SWITCH.YOUR CRUISE CONTROL SWITCH COULD BE FAULTY.BEST TO TAKE CAR TO DEALERSHIP LET THEM HOOK CAR. TO DIAGNOSTIC EQUIPMENT.BECAUSE CRUISE CONTROL IS ELECTRONIC AND PCM CONTROL.THE CRUISE CONTROL SYSTEM USES INPUTS FROM VSS SENSOR .SO IT WOULD BE HARD TO FIX AT HOME YOU NEED EQUIPMENT TO FIX AND TROUBLE SHOOT.

only one item on this car will cause this which is the cruise contro module

best thing to do is get a scanner reading to see if anything is showing to be defective. but first do a visual inspection for any problems around the cruise control. do you know what to look for? please reply

how low of a speed? Some cruise controls won't work under 35mph

Your model may be under the recalls. There was a mass recall for Ford controls and the dealers added a inline fuse under the hood by the cruise control box.