The constant control relay is a box located under your air filter. Inside are normally about 5 relays. One of the main reasons it goes out is because of issues with the WAC relay due to overheating or poor soldering on the circuit board.
To replace, remove air intake from front, right end of vehicle (drivers side). You will see the CCRM beneath. Socket wrench required.
Find the letter and serial number located on it and replace. It solves the no a/c issue and it also solves the engine start and fan relay issue for the radiator fan.
Expect to spend over 150 dollars for replacement from Autozone. It's closer to 200-300 dollars from Ford.