American Standard 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 ( 2 volts) [possible grounding problem]”
Documented for: *UD1 / *DD1 fan-assisted gas furnaces with 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 at or 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 American Standard 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 Furnaces, "Fan Assisted Combustion System" (18-CD19D7-17) (American Standard Heating and Air Conditioning, *UD1A/*UD1B/*UD1C/*UD1D upflow and *DD1B/*DD1C/*DD1D downflow 80% fan-assisted gas furnaces) · checked 2026-08-25