York TM9T100C16MP11 Error Code 11 Red Flashes: Limit Circuit Open 5-15 Minutes
What Does Code 11 Red Flashes Mean?
An 11 red flashes code on the York TM9T100C16MP11 means the limit circuit stayed open for more than five minutes but less than fifteen. On this board, that specific duration is interpreted as a blower failure: if the blower were moving air, the heat exchanger would cool and the limit would reclose within five minutes. Because it did not, the board assumes the blower is not running and hard-locks.
The most common cause is a failed blower motor — burned out, seized, or with a lost winding or bad capacitor — so it cannot spin or cannot spin fast enough to move air. A failed blower wheel is the other possibility: the fan wheel may be cracked, loose on the motor shaft, or clogged with debris.
This code sits in the middle of the limit-circuit escalation. It is reached after the 4 red flashes limit trip when the limit stays open 5 to 15 minutes. Had the limit stayed open beyond fifteen minutes, the board would instead show 5 red flashes, which points to a rollout switch rather than the blower. The furnace will not restart until the problem is fixed and power is cycled off and on.
What You'll Notice
- The furnace overheats and shuts down, and little or no warm air circulates.
- The blower does not run at all, or runs very weakly.
- You may hear the blower motor humming or buzzing without spinning.
- The board shows eleven red flashes and the furnace will not restart on its own.
- It may follow repeated 4 red flash limit trips.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Failed blower motor | Most common | ✗ Call a pro → |
| Failed blower wheel | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician verifies whether the blower motor runs, tests the motor and its capacitor (or the module on an ECM motor), and inspects the blower wheel for breakage, a loose set screw, or obstruction. Once airflow is restored and the limit switch is confirmed to reclose, the technician cycles power to clear the hard lockout.
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:
- The furnace overheats and the blower does not run or barely moves air, with eleven red flashes
- You hear the blower motor humming but not spinning
- The furnace will not restart until power is cycled and keeps re-locking
- There are unusual rattling or grinding noises from the blower area
Frequently Asked Questions
What is the difference between 11 red flashes and 5 red flashes?
Eleven red flashes means the limit circuit stayed open 5 to 15 minutes, pointing to a blower motor or wheel failure, while 5 red flashes means it stayed open more than 15 minutes, pointing to a rollout switch.
Why won't my furnace restart after 11 red flashes?
It is a hard lockout. The furnace will not restart until the blower problem is repaired and the power is cycled off and back on.
Can I fix 11 red flashes myself?
No. Blower motor and blower wheel diagnosis and replacement require a technician.
Sources
✓ Verified against manufacturer service manual — March 2026