The cruise control light will come on but when I go to set it, it doesn't engage. I don't have a problem with my horn not working or anything else. Could there be a problem with the set button or is there something that I'm missing?

 

my father in laws dosent work some times and if we wiggle the switch in a circle it will come on ..possibly just worn contacts in combo switch

 

May also be the brake switch on the pedal. Should be two on there, one for the high mount and one for the normal ones. If the cruise thinks the brakes are on, it will turn on but not set.

No idea if the Dodge is affected by this, but on Chevy GMT800 trucks if you replace the high mount brake light with an LED light, the cruise will no longer work. The cruise uses the high mount switch as it's brake on trigger, and when you start the engine it does a resistance check on the circuit. If the resistance level is wrong, it assumes the switch is broken and won't allow the cruise to work. A resistor in line with the high mount brake line solves the problem by putting the correct resistance back in.

 

yes the button can, and usually is, worn out.