Heater problem

Make sure the coolant is full. If it is full, the engine is running at a normal operating temp, check the following. First, start the engine, open the hood, allow the engine to warm up, and have the heater on high. When the engine is hot, feel both heater core hoses. Both should be hot. If one isn't, then the coolant isn't flowing through the heater core. Flush the core to see if that helps. If both are hot, have the blend air door in the vehicle checked. It is located near the heater core. It is a vent door that determines if you get AC or heat into the vehicle.