heat don't work on 1999 Lincoln Navigator

The blower is blowing but heat won't get warm, it is cold. What could this be?

2 answers 1 comment
It could be in the Electronic Automatic Temperature Control (ETAC) unit in the dash, the thermostat could be not functioning and the engine is running cold, the coolant level could be too low and there's therefore air in the heater hoses, it could be a kinked or blocked heater hose,
If you don't see anything obvious and you want a shop, I've included a directory link for you:
Your heater blend door is likely broken. Go to www.heatertreater.net for replacement parts and instructions! MUCH cheaper that having a dealer do the repair!! I just did mine.