I always feel air coming out of the even when the vent is turned off.

 

You cant unless you put a switch on the fan motor. Chevrolet's/GM have been using that ventilation system for years. That way if there is an exhaust leak, you wont get dizzy, fall asleep at the wheel, or die from carbon monoxide poisoning. BTW I have never had a cabin fan fail on me yet. Why do you want to disable it?

 

my 04 wbody is like that...try putting it into recirc mode.

 

I want to stop the air flow because during summer the air coming is hot. And during winter is cold. I have had other cars (other brands) and I always could isolate the cabin from air coming in.

 

As Tech2 said you can use the re-circulation mode to keep the outside air from coming in. I suppose you could block off the cabin air-filter as well with some cardboard.

I am not understanding your remarks, because you will still get hot in summer if you dont use the A/C. Are you trying to save gasoline by not running the AC?

Should be a fuse for that, or you could unplug your Freon low-pressure pressure switch so AC compressor wont come on. As to winter cold, using the heater doesn't decrease gas mileage as there is no pump that uses power to run the heater beside your water pump.