Trane Furnace 9 Flashes
WarningShown as: 9 flashes, pause, repeat
The control is directing the technician to check the igniter circuit and the voltage between line neutral and 24VAC common, which points at an igniter or grounding problem.
Manual wording: “9 Flashes --- Check Ignitor circuit and Line "N" to 24VAC "Common" voltage (< 2volts) (possible grounding problem)”
Documented for: *UH1 / *DH1 condensing furnaces (XR 95 family) and other Trane furnaces using the LED-only integrated furnace control
Likely causes, most common first
- Igniter circuit fault
- Possible grounding problem (Line "N" to 24VAC "Common" voltage should be under 2 volts)
What you can safely check yourself
- Note whether the furnace tries to start and never lights
When to call a technician
Call a technician. Checking the igniter circuit and neutral-to-common voltage requires meters inside a live control compartment.
A Trane furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Installer's Guide - Upflow/Horizontal, Downflow/Horizontal, Gas-Fired, Direct Vent Condensing Furnaces (18-CD29D1-14-EN) (Trane, *UH1B/*UH1C/*UH1D upflow and *DH1B/*DH1C/*DH1D downflow condensing gas furnaces (XR 95 family; first letter A or T)) · checked 2026-08-25