Furnace Fault Codes

Furnace flashing 2 times: what 2 flashes means

The number of flashes on a furnace control board is not a standard. Every manufacturer assigns its own meanings, and 2 flashes means something different on each of the 5 control families below.

These are not variations on one fault. They are entirely different problems, and the count alone does not distinguish them. Identify the manufacturer before acting on any of them.

2 flashes, by manufacturer

Furnace brandWhat 2 means there
Armstrong
2 flashes		Improper earth ground
Goodman
2 flashes		Pressure switch is closed when it should be open
Heil
2 flashes		Low pressure switch closed when it should be open
Rheem
2 blinks		Pressure switch failure — switch remains open
Trane
2 flashes		System lockout — retries or recycles exceeded

Finding out which brand you have

The brand is printed on a rating plate inside the furnace cabinet, usually on the inner wall behind the removable front panel, and often repeated on a sticker on the outside of that panel. The name on the thermostat is not reliable — thermostats are replaced far more often than furnaces, and a great many furnaces are sold under a different name from the company that built the control board. The brand hubs below list the alternative names each manufacturer sells under.

If the furnace shows a number rather than flashes

Several manufacturers stopped using flash counts and display a two-digit status code or a letter-and-digit code on a seven-segment display instead. If what you are reading is a number on a small screen rather than a light going on and off, count nothing — read the code directly and look it up on the manufacturer's page.

Other flash counts

Sources

Every meaning on this page comes from the manufacturer document behind its code page:

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.