2003 Ford Explorer Q&A
2003 Ford Explorer Question: heater making noise and not blowing hot but cold air
You almost certainly have a failed temperature blend door actuator. The dash must be accessed to replace it. The tell-tale sign is the clicking noise when trying to change the temperature from where it sits now. Beware: some of these also had cracks in the heater plenum (the box that has the doors and houses the heater core, etc). These cracks also exhibited a repetitive click noise and would not adjust the temperature. However, replacing the motor does not fix it. Still, the more common fix is the temperature blend door actuator. - DaveJHM
either your heater core or thermostat is shot for the heat part, the clicking could be the blowermotor is going or something is sticking on the motor causing it to click - sparky8265
What if you go to turn on the heater and it makes a real loud noise and blows out cold air? when it turned to cold air it does not make the noise. Its like in the flapper that switches it hot to co...