Status LED flashes 13 times; furnace may lock out after repeated limit trips

Safety first: Turn off power before checking limit switches or wiring.

• Locate all limits: Identify the main high limit on the heat exchanger panel and any auxiliary limits on the blower deck or near the burners. Check for loose or burnt connectors.
• Continuity test: With power off, disconnect one wire from each limit and test for continuity. All normally closed limits should read closed at room temperature.
• Correct airflow problems: Replace filter, open registers, and ensure return air is not blocked. Check blower speed tap settings on the control board per Rheem wiring diagram.
• Reset lockout: Cycle power to clear the code. If limits test good and airflow is adequate but the code returns, the control board may be faulty.

Do not bypass any limit switches; they are essential safety devices.