No heat my mechanic said it was some electrcal not connected but what

No heat and a clicking in the dash almost always indicated a bad blend door actuator. Its an electric motor that opens a door to direct air flow over the heater core. There are a few through out the vent system behind the dash. In some cases the dash needs to be removed to access the actuator. You don't necessarily need to go to the dealer for this. Here is a link to find a good independent shop near you. https://repairpal.com/repair-shops Good luck Alex