My camrys heat was working one day and i heard it making a whiseling noise. not thinking anything of it next time i went to use it , it was blowing cold. occasionly it blows hot but that is mainly when i go around turns. It may be the heatercore not sure but like i said it still blows hot sometimes.. I went and bought another thermostat and that did not seem to fix it...I have no freaking clue anymore...