check your coolant level
check belt maybe slipping Be sure the coolant level is full
That can happen when the starter has failed.
The fuse blows because the current through it exceeds the rated current limit of the fuse.
I had the same problem...until I had the coolant in the AC system recharged two years ago
get a new heater switch
Your coolant level is low.
Low coolant in the system. Defective heater control valve. Clogged heater core.
underneath the dashboard on the passenger side.
Most likely cause is a failed engine thermostat.
Sounds like a bad water pump, or belt is slipping for water pump. Low coolant, stuck thermostat, etc.
The heater valve could be failing to open for one reason or another.
Low coolant? Thermostat not opening? Control cable not working? Plugged heater core? Heater core "airbound"? Low coolant? Thermostat not opening? Control cable not working? Plugged heater core? Heater core "airbound"?