Rheem furnace 1 blink: Soft lockout, one hour
One blink means the control has put itself into a one-hour soft lockout. It will release automatically, which is why the furnace appears to work briefly every hour and then stop.
- Limit circuit is open — Rheem, Ruud and Weather King *RC 92+ full size upflow and *RL 90+ full size downflow condensing furnaces, per installation instructions 708503a
Applies to: Rheem standard gas furnaces. Rheem states these codes do not apply to modulating, LXE, or two-stage models, which use different diagnostics. Ruud and Weather King furnaces of the same generation share the platform.
What it means
A soft lockout is a deliberate pause rather than a permanent shutdown. The control has met a condition it will not keep retrying immediately, so it stops for an hour and then tries the whole sequence again. That timing produces a distinctive and frequently misread symptom: the house gets a short burst of heat roughly every hour. People often describe this as the furnace working intermittently or struggling in cold weather. It is doing neither — it is failing, waiting out its lockout timer, and failing again in the same way. Recognising the hourly rhythm is the fastest way to tell a soft lockout from a furnace that is genuinely cycling.
Most common causes
- Repeated failure to establish or prove flame, which is the most common route into a soft lockout.
- No gas reaching the burners — a closed valve, an empty propane tank, or a supply interruption.
- A failed hot surface igniter.
- A flame sensor coated with oxide, so a real flame goes undetected.
- Low or unstable gas pressure.
- Poor grounding, which breaks the flame rectification circuit.
- A safety condition the control has chosen to retry on a timer rather than immediately.
How to diagnose it
- Note the hourly pattern. Heat roughly once an hour is the signature of this code and rules out several other explanations.
- Check whether other gas appliances work, which separates a supply problem from a furnace problem.
- Check the furnace's manual gas valve is open, and on propane that the tank has fuel.
- Watch a start attempt if the furnace has a sight glass. Whether the burners light at all is the key split.
- Note whether the blink count is genuinely one and not a longer pattern, since Rheem's standard code set is short and adjacent counts mean very different things.
How to fix it
- Restore the gas supply if that is the cause.
- Igniter replacement, flame sensor cleaning, and gas pressure testing are technician work.
- Do not reset the furnace repeatedly to clear the lockout. Each reset starts another sequence that may deliver gas to a burner that will not light it.
- Book service rather than living with hourly heat through a cold spell. The furnace is not coping — it is failing on a schedule.
Do it yourself or call someone
The homeowner share of this fault is small and specific. Confirm the manual gas valve at the furnace is open, confirm other gas appliances in the house work — or that the propane tank has fuel — and confirm the pattern really is hourly rather than random. If the gas supply was the problem, restoring it ends the lockouts and nothing else needs doing. Everything past that point — igniter testing, flame sensor cleaning, gas pressure measurement, grounding checks — happens in or around the burner compartment of a furnace that is actively retrying ignition every hour, and it belongs to a licensed technician. The one thing not to do is treat the reset as the repair. Every reset, and every hourly retry, runs another sequence that opens the gas valve over a burner that has already demonstrated it cannot light reliably. One deliberate reset after fixing an obvious supply problem is reasonable. A second lockout means stop and book the visit.
Notes
Rheem explicitly scopes this code set to standard furnaces, excluding modulating, LXE, and two-stage models. Reading a two-stage Rheem furnace against this table will give the wrong answer, so the model matters before the count does.
Related
All codes for this manufacturer
Rheem, Ruud and Weather King furnace blink codes — every code, with what differs between models.
Not sure this is your brand?
The same count means something else on other furnaces. What 1 flash means on every brand puts them side by side.
The same lockout on other brands
An hour-timed lockout after failed ignition is one of the most standardised behaviours in furnace controls, even though the codes differ. On Goodman GMEC96-family boards the same retries-exhausted, one-hour lockout reads seven red flashes, and York UTEC boards show seven red for it — two code tables this site documents as near-identical, from a shared board lineage. Carrier's 58MCB control stores the same state as code 14, ignition lockout. If the furnace in front of you turns out not to be a Rheem-platform unit, those are the pages to compare.
What the fix costs
The repair behind a soft lockout is usually one of three, and they price very differently. Flame sensor cleaning runs $80–200 — the furnace repair cost guide calls it a ten-minute job and the classic easy fix. A failed hot surface igniter runs $150–350 installed on a standard visit; the part itself is only $20–60 for a universal silicon nitride igniter or $40–120 for brand OEM, rising to $250–500 for an after-hours emergency install, per the igniter replacement cost guide. Gas pressure and gas valve work sits at $300–900, and the valve is never a DIY part. A diagnostic visit is typically $75–150, often credited against the repair. Because one blink names a behaviour — locking out hourly — rather than a component, expect the diagnosis to decide which of those you are actually buying.
What this looks like
From the outside, this usually shows up as the vents blowing cold air on a heat call — that walkthrough covers what to check in order, and when it stops being a homeowner job.