I have a very basic ford ka 54 reg. Only about 33,000 miles on clock. On warm or hot days when selecting the cool air option on the dial, It starts blowing out cool air but then starts throwing out hot air. forcing me to turn it off and suffering a roasting hot car. Damn nuisence! It can't be the fuse as i can hear the blower motor clearly when turning blower on. Anybody got any idea whats going on and can i easily rectify this problem myself? Thanks.