What would cause the heater to not blow air that is very hot? The amount of air seems right but it is just not very warm and seems to take a long time to defrost the windwhield. I don't have a leak on the floor like I have seen with a leaking heater core, is there a valve or something that could be blocked or is the heater core just going bad? If it is the heater core, how difficult are they to replace on a 98 F150 with 4.6 and automatic?Thanks, Kerwin

 

Might be the thermostat hung open. That would be the cheapest repair to start.

 

Agreed.

 

Thermostat or possibly a blend door actuator/door issue. The doors love to break on those models and the actuators don't last forever.

 

Probably justa bad blend door actuator. It is easy enough to replace, as it sits on the bottom of the case, just above the tunnel.

 

coolant level?????