Need Help for 2005 Toyota Sienna. I drove this car for almost three years I never had any problem with the Heater or the air condition. now a few day's ago when I tried to on the heater on fires for 30 second I feel heat and immediately it changes to cold since then I tried every four or five hours it is the same. I never heard any sound or any sign just like this. So please if you have same experience you can help me.