90 F150 heater blows cold
 

I need help. I have replaced the heater core and radiator thermostat. The engine operates at the correct temp but the heater blows just barley warm air. What do I check next?

Make sure it is FULL of coolant, if so check the heater hoses to see if they are getting hot, at least as warm as the upper radiator hose.

If all is good there you may have a blend door disconnected/broken under the dash..

Both heater hoses get hot. Is there a common problem to look for with the blend door/ controls?