Morning, I have a 2006 dodge stratus sedan. When I turn the heat on only cold air blows when the car is sitting at a red light. But when I drive hot air blows. Is my heating element going out?

Water-cooled engines supply heat for the passenger compartment by circulating hot coolant through a radiator-like heater core. The passenger compartment fan forces air through this heater core and into the passenger area. The flow of coolant for this purpose can be controlled with a valve in the line that is adjusted when the heat control is moved or via a flap that blocks or opens the air path through the heater core to adjust temperature.
The effect you describe can be caused by several different sources:
- A slipping belt which turns the water pump. - A partially collapsed hose in the circuit for the heater, causing a reduction of water flow to the heater core. - A heater core internally blocked from deposits from the water component of the coolant. - A valve which is not being adjusted through its normal range by the dashboard control. - A flap suffering the same limitation as above.
Another effect our personal vehicles generally show with age is caused by abnormally low engine friction attributable to a particular additive we use that reduces engine friction so much that the thermostat that controls coolant/engine temperature is wide open but the engine doesn't heat enough to bring the coolant temperature into the normal operating range. We notice on two of three vehicles, that rolling on a long downgrade (engine not loaded) will cause the engine temperature to drop below its customary operating temperature.
If you have a dashboard temperature gauge, watch it to see if it rises into the middle of the range or not. If not, there may not be much you can do other than flush the cooling system, making sure that the heater control is set to its highest temperature to ensure that the heater core is in the loop while flushing.