汽车没开暖气和吹风，但一开车，就有热风倒灌进来

汽车没开暖气和吹风，门窗紧闭，但一开车，就有热风倒灌进来，这是咋回事啊？
另外，汽车启动时，总是听到嗡嗡声，启动好了，这种声音就消失了。
谢谢点拨。

所有跟帖： 

• turn the temp selection knob to far left (cold)... -internuts- ♂ (47 bytes) () 09/19/2009 postreply 06:48:03

• Duct gate is not in proper position -biglow- ♂ (375 bytes) () 09/19/2009 postreply 07:35:29

• thanks. my car,,, -xwq97ud- ♂ (169 bytes) () 09/19/2009 postreply 09:46:37

• my camry has the same problem co ask -boarding- ♂ (0 bytes) () 09/19/2009 postreply 13:04:30