It could be low coolant or it could be that the water pump impellers are rusted or worn through.
Get the air out of your heater core.
heater hoses might have been disconected
probably the heater core is plugged
Its either a bad heater core or a clogged one. They are very expensive.
thermostat
There is no heater fuse, the heater works by having hot coolant run threw a heater core that's inside the dash, then when you turn the heat on, the blower motor blows threw the heater core, sending the hot air inside the vehicle.
Although my car is not an Eclipse, I experienced the same issue. A mechanic determined that my radiator was partially blocked and recommended replacement. My heater now blows heat whether I'm stopped at a light or moving.
I have changed heater core,water pump,thermostat, the fon works well but only blows cold air plus i have flushed the system.
Same way the heater on your truck works... coolant is run through the engine system, becomes heated, is run through a heater coil, and a blower blows the heated air around the heater coil through the ductwork to heat up the vehicle.
thw wind works by god blows the wind thw wind works by god blows the wind
sounds like you need to replace either the thermostat or the temp control switch
[first time answering questions] car heater works like the reverse of the normal cooling radiator - in fact the heater is like a small version of the rad that's on the frnt of the car - the hot water from the engine block goes into this small rad and the heater fan blows air thru it into the car - the hot heater rad loses heat into the car and - bingo - you get warm inside