[caddyman379]

It could be a plugged heater core, or the blend doors could not be moving. When you slide it over to hot, can you hear them move? Some cars you can't hear it at all, but most you can.

Feel the rubber heater core hoses once the engine's warm, is one side hotter than the other? Are both cold?

Im assuming you've checked the coolant level?

Do that and report back.