It could be a few things. First, confirm the engine coolant is full. Also, take a look through this link and see if anything helps:
Next, try this and let me know the results. Allow the engine to warm up to operating temp with the heater on high. Once operating temp is reached, turn the engine off and carefully touch each of the two heater hoses where they attach near the firewall. Both should be hot.
If they are hot, then suspect a blend air door actuator isn't working. If the coolant is full and only one hose is hot, suspect the heater core is plugged.
Let me know what you find or if you have other questions.
Monday, May 25th, 2020 AT 7:49 PM