2004 Toyota Corolla

Heater problem
2004 Toyota Corolla 4 cyl Front Wheel Drive Automatic 140000 miles

My heater on my 2004 Corolla would not work this morning. It worked fine last night. Its also 24 degrees outside its our first time in the cold (the car and I) and Idk what could be the trigger. Could something be frozen?
Could it be a fuse?
December 30, 2009.

You can buy a coolant tester from most autoparts stores for $5. Test coolant in radiator or coolant recovery tank (radiator is best), coolant should test at least -30F.

If original coolant (Toyota coolant is red in color), it should be changed every 24000 miles.

Next check heater core hoses, both should be hot at operating temp. If not hot, then thermostat.
If hot, then divertor valve.

Best advice is to get car into garage to thaw and then see if heater works, if it does, then get coolant flushed and changed, DO NOT let this engine overheat.

Dec 30, 2009.