Furnace starts normally but shuts off before reaching set temperature; thermostat still calling for heat

Safety first: Turn off power before accessing internal components.

• Replace filter: Install a clean filter and ensure correct airflow direction.
• Inspect evaporator coil (if present): Look for dust or ice restricting airflow. Have it professionally cleaned if dirty.
• Check temperature rise: A technician can measure temperature rise across the furnace and compare to Rheem nameplate. Excessive rise indicates airflow problems.
• Test limit switch: If airflow is good but the limit opens prematurely, replace the high limit with the correct Rheem part.

Do not bypass the limit switch; it protects against overheating and fire.