The other day when it was just a little chilly outside we turned the heater on and it worked fine. This morning while it is 44 degrees the heater would not get warm at all. The fan would blow fine. The engine temp is at normal temp. l just do not understand what could be wrong. Can anyone help?

Look in your floor board and see if it is getting wet on the passengers side,sounds like the heater core is going out in it.

When you turn the temp control for the heater do you happen to hear a clicking type noise? if you do this is a sign of the blend door motor that opens and closes the temp door in the dash going bad, even if you do not hear it l would assume this is your problem l have replaced a great number of these, if you remove the radio you can see this white square shaped motor attached to the heater box, when you turn the temp control know this motor should turn back and fourth