Rheem, Ruud and Weather King furnace blink codes

Rheem's standard gas furnaces use a short list of blink codes — but Rheem is explicit that they do not apply to modulating, LXE or two-stage models, which diagnose differently.

Also covers: Ruud, Weather King — same manufacturer, same controls, same codes.

Rheem, Ruud and Weather King are the same manufacturer. Their standard gas furnaces use a compact set of blink codes, one through five, covering soft lockout, the two pressure switch failure directions, the limit switch, and a twinning circuit fault. Because the list is short, adjacent counts carry very different meanings and counting accurately matters more than on manufacturers with longer code sets.

Worth knowing before you count

Rheem states these codes exclude modulating, LXE and two-stage models. Reading a two-stage Rheem furnace against this table gives the wrong answer, so establish the model before the count. Rheem also documents that the five-blink twinning code can appear on some installations using an electronic thermostat, with no twinning present at all.

Rheem, Ruud and Weather King

1 blink — Soft lockout, one hour
2 blinks — Pressure switch failure — switch remains open
3 blinks — Limit switch open
4 blinks — Pressure switch failure — switch remains closed
5 blinks — Twinning circuit failure

Other manufacturers

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.