Heat is on but only blows cold air.

I recently bought a 99 eclipse and it only blows cold air. How do I know which part to replace. The radiator had already been replaced. I figure it has to be either the thermostat, blower motor or heater core. How do i find out which one without having to buy all 3

If the blower fan works, it's ok. It does not control temp. When the car is warmed up, check feel the hoses going to the heater core. If they are both hot, it's ok, If one hose much cooler than the other one, the core is plugged. You can try to backflush the core before you replace it. If the stat has not been replace recently you may want to do that also. You also need to make sure that the temp control door is working properly.

If the blower fan works, it's ok. It does not control temp. When the car is warmed up, check feel the hoses going to the heater core. If they are both hot, it's ok, If one hose much cooler than the other one, the core is plugged. You can try to backflush the core before you replace it. If the stat has not been replace recently you may want to do that also. You also need to make sure that the temp control door is working properly.


Couldnt have said it better myself