York TM9E furnace 4 red flashes: Main Limit Open
Try DIY first, then call a pro
What do 4 red LED flashes mean on a York TM9E furnace? The main limit switch is open, and the supply blower and inducer keep running while it stays open. Five openings in one heat demand cause a 1-hour soft lockout; if it stays open past 5 minutes, the code changes to 11 red.
Before you touch anything: the six signs that mean stop troubleshooting and call a pro →
Safe checks before calling
Check the external air filter and replace it if clogged, following its instructions. Make sure supply registers and return grilles are open and clear. Do not open control compartments.
If the filter and vents are clear and the code returns, a technician should check airflow, the blower, firing rate, temperature rise and the limit circuit. Never bypass the limit.
Possible causes
- Restricted airflow from a dirty filter or blocked registers DIY-CHECKABLE
- Blower, firing-rate or temperature-rise problem found by a technician TECH
Parts for this code
No model-verified part number is listed here. Have the fault diagnosed and the correct part matched to your furnace before ordering.
Questions about this code
What do 4 red LED flashes mean on a York TM9E furnace?
The main limit switch is open, and the supply blower and inducer keep running while it stays open. Five openings in one heat demand cause a 1-hour soft lockout; if it stays open past 5 minutes, the code changes to 11 red.
How do I fix York TM9E furnace 4 red flashes?
Clear any filter or vent restriction first, following the filter instructions. If the limit opens again, hits the 1-hour soft lockout, or advances to 11 red flashes, schedule overheating diagnosis rather than repeated restarts.
How much does it cost to fix York TM9E furnace 4 red flashes?
A dirty filter may be the only expense if it caused the restriction. Recurring trips require airflow, firing-rate and limit-circuit diagnosis before any parts are priced.
Related symptoms
These symptoms can appear alongside this code. The link is an association, not a diagnosis, and code meanings vary by brand, model and control.
Applies to
TM9E
Different York generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Verified against YORK TM9E Series Installation Manual — Single Stage ECM Residential Gas Furnaces, p.33
Verified against YORK TM9E Series Installation Manual — Single Stage ECM Residential Gas Furnaces, p.34
Last verified 2026-10-07 · page updated 2026-10-07 · how we verify
Related York furnace codes
These codes use the same york tm9e single-stage ecm tri-color led control system.