Furnace displays E07 and will not start, or stops shortly after starting.

Safety: Disconnect power before inspecting internal components.

Steps:

• Check return grilles: Make sure all return air grilles are open and not blocked by furniture, dust, or filters.
• Inspect circulation fan speed: Verify that the fan is running at the correct speed during heating. If it seems slow or noisy, the motor or capacitor may be failing.
• Clean internal filters: Some Cointra furnaces have internal mesh filters. Remove and clean them with a vacuum or mild soap and water, then dry completely before reinstalling.
• Check return NTC sensor: Locate the return temperature sensor on the return air side. Ensure it is firmly attached and not touching hot components. Replace if suspected faulty.

Professional service: A technician should verify airflow, fan speed settings, and confirm that the furnace is correctly sized and ducted for the installation.