HVAC Code Lookup

American Standard Furnace: 8 Flashes

Code 8 Flashes: Low flame sense signal

WarningShown as: 8 flashes, pause, repeat

Low flame sense signal. The furnace is running but the flame current the control reads is weak.

Manual wording: “8 Flashes --- Low flame sense signal”

Documented for: *UD1 / *DD1 and CUB1 / CDB1 fan-assisted gas furnaces with the LED-only integrated furnace control

Likely causes, most common first

  1. Low flame sense signal

What you can safely check yourself

  • Note whether the furnace is still heating; this code usually appears while it is still running

When to call a technician

Schedule service. A weak flame signal usually means the flame sensor needs cleaning or the burner flame is not right, and if it drops further the furnace will lock out. Cleaning a flame sensor means working in the burner compartment, so leave it to a technician.

A American Standard furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Full page for American Standard code 8 Flashes

Other American Standard codes