Heater blows only cold air all of a sudden. on 2002 Pontiac Aztek

The heater worked fine last week, but now the air will not get hot. It blows strong but stays cold. What are the possible causes?

by in Duluth, GA on October 04, 2010
1 answer
ANSWER by , December 06, 2010
plugged heater core, low coolant, stuck heater control, thermostat.