Q: Engine is getting warm, heater is only blowing warm air when the vehicle is moving. 2003 Jeep Grand Cherokee

Hi there - this sounds like a possible thermostat (no allowing proper warm-up to operating temperature), or an inadequate water flow (water pump or clogged radiator) problem. The lack of heater function could have 5 causes: the engine is not getting up to correct temperature (center of the gauge) due to a malfunctioning thermostat, the heater control valve is not letting enough hot coolant into the heater core, there is a restriction in the heater system that is preventing adequate hot coolant flow through the heater core, the heater fan is not working to transfer heat from the heater core to warm air for the passenger compartment, or the air blend doors inside the heater are not working properly to route warm air to the desired vents. I would recommend a heater system inspection](https://www.yourmechanic.com/services/heater-is-not-working-inspection) by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.