my 2000 4runner has been great with 202K miles on it now, until it was cold one day in south florida and when the heat kicks in there is a clicking noise under the glove box and to the left and when it is clicking you get no heat. i believe this is the vent to let the heat thru from the engine compartment and it can't open anymore. so i gotta crank the a/c to a cold temp to get it too stop, real annoying, can anyone tell me what is involved in fixing this or how much it will cost?