1999 Mercedes-Benz ML430 Q&A

1999 Mercedes-Benz ML430 Question: In my 1999 ml430 when I turn on heat it blows cold air what can I do

I changed cabin filter still blows cold air what's next -
Answer 1
Replace the thermostat, it is probably stuck in the closed position. -
Comment 1
Where is thermostat -
Answer 2
could be blend door stuck open -
Comment 1
What is a blend door??? -
Comment 2
It's a door inside the HVAC housing that controls the airflow through the heater core and A/C evaporator , to regulate air temp. Cabin filter - filters air. Stuck closed thermostat would cause overheating. CHECK coolant level first , and make sure the engine is reaching proper operating temp. -