Hello.

If everything appears to be working correctly but the air blowing out just isn't hot, that's almost always an obstruction of some sort in the coolant flow.Start the car, let it warm up to normal operating temperature and then check the two hoses that go into the back of the heater core to see if they are hot. They should feel about the same as the upper radiator hose.If no, then something is blocking the flow. Don't take this the wrong way, but you did take those little caps off of the heater core tubes before you attached the hoses, didn't you?

It can happen.Hope that helps.
