Why wont my heat get hot like other cars? I replaced me heater core back in the summer and now thats its cold out I have 2 problems. 1st my heat doesnt get very hot. The other mustang I owned and my friends mustang's heat always got hot and it didnt take 20min to do so like mine does. I mean it gets warm, but I dont like being cold and I need it to be HOT. and my other problem is that my blower only blows if the knob is on the highest setting. If I put it on any other setting the blower doesnt come on at all. I replaced the blower switch and it didnt help.