What does York code 9 Blinks mean?
York furnace code 9 Blinks means the furnace detected reversed line polarity or an improper ground on the supported control family. Confirm the model number and diagnostic chart inside the furnace door before replacing parts.
What causes York code 9 Blinks?
- Reversed line and neutral wiring
- A missing or poor equipment ground
- Incorrect transformer phasing on twinned furnaces
Can I troubleshoot York code 9 Blinks?
- Turn the furnace off at its service switch.
- Do not alter line-voltage wiring or grounding connections yourself.
How much does York code 9 Blinks cost to fix?
A control board replacement typically costs between $150 and $500 nationally.
When should I call a technician?
Call a licensed technician or electrician to verify polarity, grounding, and supply voltage.
Sources and model scope
Fault codes vary by model and control board. Confirm the diagnostic chart inside your furnace panel or the official manual before acting.
Scope used here: Johnson Controls integrated furnace controls using the documented 1–12 red-flash table.
- Johnson Controls Unitary Products: Gas Furnace Installation Manual
272441-UIM-E-0513 · Johnson Controls integrated furnace controls with the 1–12 red-flash table in this manual; other model families may differ.
Compiled by Warmlo Editorial · Reviewed August 2026
This is general information, not professional advice. Gas, electrical, and combustion repairs can be dangerous — when in doubt, call a licensed technician.