York TM9V080B12MP11 Error Code 5 Red Flashes: Limit Circuit Open Over 15 Minutes
What Does Code 5 Red Flashes Mean?
When the limit circuit remains open for more than fifteen minutes, this York board stops interpreting it as ordinary overheating and instead assumes a manual-reset rollout switch has opened. Rollout switches are placed to catch flames or heat spilling out of the burner or heat-exchanger area rather than following the normal path. Because that points to combustion escaping where it should not, the board enters a hard lockout: the furnace will not restart on its own even after it cools.
The manual directs a check of combustion air supply, inducer operation, and the primary heat exchanger or burner. A cracked or failed primary heat exchanger, a burner problem, or inadequate combustion air can all cause flame rollout that trips the switch. On a condensing furnace, restricted combustion-air intake or a venting problem can contribute as well.
This is the fifteen-minute end of the same limit-circuit escalation that begins with the 4 Red Flashes overheating code and passes through the 11 Red Flashes code at five-to-fifteen minutes (assumed blower failure). Five flashes is the most serious of the three because of the rollout and heat-exchanger implications.
What You'll Notice
- The furnace runs for a while, then shuts down completely and will not restart automatically.
- A rollout switch on the burner assembly has tripped and may have a popped manual-reset button.
- You may notice a hot, burnt, or unusual odor near the furnace, or signs of soot around the burner area.
- Cycling the thermostat does nothing because the board is in hard lockout.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Manual-reset rollout switch has tripped | Most common | ✗ Call a pro → |
| Primary heat exchanger failure or burner problem | Common | ✗ Call a pro → |
How This Is Diagnosed
This is diagnosed by a technician because of the safety implications. They inspect the primary heat exchanger for cracks and the burners for flame disturbance, verify adequate combustion air and proper inducer operation, and confirm what caused the rollout switch to open before resetting it. Only after the underlying cause is corrected is the rollout switch's manual button reset and power cycled to clear the hard lockout. Because a cracked heat exchanger can introduce combustion gases including carbon monoxide into the home, running the furnace before this is resolved is not advised.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- This code appears and the furnace is locked out — treat it as urgent.
- You notice a burnt smell, soot, or a tripped rollout button near the burners.
- Anyone in the home reports headaches, nausea, or dizziness while the furnace runs — leave and call for help, since carbon monoxide is a risk with heat-exchanger faults.
- The furnace was recently short-cycling or throwing overheating (4 red flash) codes before this appeared.
Frequently Asked Questions
Why won't my furnace restart after a 5 red flash code?
The board has entered a hard lockout because the condition points to a rollout switch trip and possible heat-exchanger problem. It will not restart until a technician corrects the cause, resets the rollout switch, and cycles power.
Is a 5 red flash code a carbon monoxide risk?
It can be, because a cracked heat exchanger or burner problem can trip the rollout switch and also let combustion gases enter the home. Have it inspected before running the furnace, and make sure your CO alarms work.
Can I just reset the rollout switch myself and keep using the furnace?
No. Resetting the switch without finding why it tripped can be dangerous. A technician needs to inspect the heat exchanger, burners, and combustion air first.
✓ Verified against manufacturer service manual — March 2026