eclipse almost no heat from vents

i'm new to owning an eclipse and i have an issue that is bugging me right now especially because it winter and cold. it is an 01 eclipse gs with the 2.4 liter engine and 5 speed. it runs and warsm up to operating temperature just fine. he engine does not over heat or anything like that. onced warmed up on the drivers side of the vehicle i get very cold air coming out of the vent. as you move to the passenger side of the vehicle the other 3 vent go from kinda cold, to luke warm, to hot on the very right side of the car. what could be causing this?

i've heard a bad thermostat, plugged lines, plugged heater core or even a bad heater core, bad coolant, and even a bad engine. i bought the car like this and the previous sad that he had replaced the thermostat and coolant. im just wondering if anybody else has had this problem and what they have done to fix it?

First thing I would check are the 2 water lines going to the heater core once the engine is warm. They both should be hot, if only one is hot and the other is only warm then the heater core is clogged. Since half of your heat works Im thinking there is somo blockages in the heater core. The easiest thing to do is drain the coolant in the motor and flush the heater core in the opposite direction that water normally flows through it. This might flush some of the trash out of it.

both heater hoses are the same temp. the feel the same and i used a temp gun on them. just a couple days ago when i rev the engine past 4 grand i can smell antifreeze through the vents. this is something new. maybe now i have a pin hole in the heater core? that wouldnt cause my heat problem would it? so part of the core could be blocked? could it also be an acuator and blend door that isnt working properly?