My 2005 Toyota Sienna Van has had intermittent AC/Heat issues for several months now. Almost half of the time when I turn the knob to turn it on, nothing happens. (The rear system works fine). Oddly enough, if I hit the top part of my glove box hard enough suddenly the AC cuts on and it's fine. Cold air is fine, hot air is fine, it's just an intermittent problem. We are constantly having to hit the glove box area very hard and suddenly it kicks in. Could it just be the fan or blower motor and is that a major expense?