1. Low Coolant Level: Ensure the coolant level in the reservoir is full. If it's low, add a 50/50 mix of coolant and water to the reservoir.
2. Faulty Radiator: Inspect the radiator for any leaks, blockages, or corrosion. If the radiator is damaged, it may not be able to transfer heat effectively.
3. Air in Cooling System: Check for any air pockets in the cooling system. Air pockets can prevent hot coolant from circulating properly.
4. Clogged Heater Core: The heater core is responsible for transferring heat from the coolant to the passenger cabin. If the heater core is clogged, it won't be able to release warm air into the vehicle.
5. Faulty Blend Door: The blend door controls the mix of hot and cold air that enters the passenger compartment. If the blend door is stuck or malfunctioning, it may not be allowing enough hot air to flow into the cabin.
6. Insufficient Coolant Flow: Check the coolant flow rate. If the flow is restricted or slow, it may not carry enough heat to the heater core.
7. Faulty Heater Control Valve: The heater control valve regulates the flow of coolant to the heater core. If the valve is stuck closed, it will prevent hot coolant from reaching the heater core.
8. Electrical Issues: Check the electrical connections related to the heater, including the blower motor, temperature control sensor, and heating control module. Loose or corroded connections can interfere with the heater's operation.
If you're not comfortable diagnosing and fixing the issue yourself, I recommend taking your Stratus to a trusted mechanic for further inspection and repair.
