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.

How Rheem furnaces signal codes

The signal itself is simple — a single status LED blinking a count, repeating after a pause — but Rheem is the brand where the count alone is least trustworthy, because two control platforms sold under the same name read the same counts differently. On the standard list, one blink is a one-hour soft lockout, three blinks is an open limit switch, and four blinks is a pressure switch stuck closed. On the *RC 92+ upflow and *RL 90+ downflow condensing furnaces, one blink is an open limit circuit, three blinks is the pressure switch stuck closed, and four blinks is a lockout after five failed ignition attempts. Only two blinks — a pressure switch that will not close — means the same thing on both. The model number on the rating plate settles it: a model beginning RC or RL, or described as a 92+ or 90+ condensing furnace, reads against the condensing list. If the model cannot be identified, treat the count as ambiguous rather than guessing.

The Rheem codes people look up most

The ignition lockouts lead: one blink on the standard list and four blinks on the condensing list both describe a furnace that tried to light, failed, and gave up — the same cold-house event wearing two different counts. Two blinks, the one count both lists agree on, is the pressure switch refusing to close, which points at the inducer and venting before the switch. Three blinks is an open limit on standard furnaces — an airflow problem more often than a bad switch — and a stuck-closed pressure switch on condensing ones, which is exactly the kind of divergence that makes the model check worth thirty seconds. Five blinks, the twinning code, deserves scepticism on any furnace that is not actually twinned.

Which Rheem furnaces these pages cover

The standard blink codes are documented from Rheem Professional Technical Support's flash code table for standard gas furnaces — which Rheem explicitly scopes to exclude modulating, LXE and two-stage models. The condensing furnace codes come from installation instructions 708503a for the *RC 92+ full size upflow and *RL 90+ full size downflow condensing furnaces, where the blink meanings are described inside the sequence of operation rather than in a labelled table. Ruud and Weather King are the same equipment under different nameplates, so both lists carry across all three brands.

What the common Rheem fixes cost

An ignition lockout — one blink standard, four blinks condensing — most often resolves at the cheap end: flame sensor cleaning runs $80–200 and is the classic easy fix, while a genuinely failed igniter is $150–350 installed with the part itself $20–60. Pressure switch codes in either direction run $150–400, and the blocked flue should be ruled out before the switch is blamed. An open limit is $150–350, with the real work being the airflow diagnosis behind the trip. If the count will not resolve against either list, a $75–150 diagnostic visit — often credited against the repair — is cheaper than replacing parts against the wrong table, and a control that has genuinely failed lands at $400–900 installed.

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

Rheem condensing furnace blink codes

1 blink — Limit circuit is open
2 blinks — Pressure switch did not close within 10 seconds
3 blinks — Pressure switch closed when it should be open
4 blinks — Lockout after five failed ignition attempts
Which blink code list applies — Rheem publishes two blink code lists that contradict each other

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.