I have a 1999 Ford Expedition 5.4L with over 140k miles on. I had my
Coolant system flush along with a new thermostat put in. I still can not
Get any heat. The air condition works fine. My system consist of an
Electronic Automatic Temperature Control (EATC). Sometimes the
System starts to put out warm air and stops and go back to putting out cold air. I need help. Thank you in advance.

This link may help:

https://www.askmehelpdesk.com/cars-t...ml#post1999642