Rheem Furnace 11 Error Code: Meaning, Causes & Fix

Failed ignition — the furnace control ran an ignition attempt and flame was not established and proved; the code is displayed after the first failed attempt and stays until ignition succeeds or the failures escalate to lockout.

Code 11 is Rheem's ignition-failure report on the 7-segment control generation, and Rheem's own ordering of causes surprises most owners: the first cause the (-)97V manual lists is not a dead igniter but the flame sense rod being unable to sense flame — the burners may light and the control still declares a failed ignition because it never saw proof of flame. The sequence around the code is fixed: after a failed attempt the inducer completes a 20-second postpurge and the control tries again, up to four consecutive attempts. Four in a row elevates the fault to the one-hour lockout, and the display then alternates '11' with '10'. On communicating (EcoNet) systems Rheem hides the first one or two failures from the homeowner display — 11 is only shown to the homeowner after at least three failures in a single heat call — but it appears in the thermostat's active-fault screen from the first failure, and it is logged into the fault buffer only once per heat call.

What causes the 11 code on a Rheem furnace?

Flame sense rod unable to sense flame (Rheem's #1 listed cause)

The rod may need cleaning or may not be properly connected. The burner can light perfectly and still produce an 11 if the rod is coated, mispositioned or its wiring to the control is open — the control never receives proof of flame inside its trial window, so it shuts the gas valve and records a failed ignition.

Gas valve turned off / no gas to burn

Rheem's second listed cause is the gas valve being turned off. The manual switch on the gas valve left off after other work, a closed manual shut-off, or an interrupted supply all produce a textbook 11: inducer runs, igniter works, nothing lights because there is no fuel.

Igniter not working properly

The igniter may not be properly connected, or the spark location may not be correct — on these Rheem controls ignition is by spark, and a spark landing in the wrong place lights nothing. A cracked or displaced igniter shows as an 11 with a healthy gas supply.

Flame not spreading from the first burner to the last

Rheem's carry-over branch: check manifold pressure during ignition (the (-)97V manual gives approx. 3.5 in. w.c. for natural gas and approx. 10 in. w.c. for LP); if pressure is good and the first burner lights but the second, third and so on do not, the burner itself may need to be replaced. Restricted orifices or gas flow belong to the same branch in the R95P troubleshooting list.

Furnace control (I.F.C.) not working properly

The last of Rheem's listed causes: the control itself fails to run or to read the ignition sequence correctly. It is diagnosed by elimination — rod, gas, igniter and carry-over proven first — and the cure is control replacement.

Line and neutral swapped (from Rheem's ignition troubleshooting)

The R95P manual's no-light list adds polarity: verify L1 and neutral are not swapped at the control and junction box — reversed polarity (fault 26's territory) can also break flame sensing, because flame rectification depends on a correct ground reference.

Checks to run before you replace anything

1. SAFETY: this is a gas appliance failing to light. If you smell gas at any point, stop — no more start attempts — and call the gas utility or a licensed HVAC technician. Never open the gas train, jumper a pressure switch or limit, or hold a gas valve open manually to 'help' it light.
2. Watch one full attempt from outside the burner compartment and note which of three stories you see: (a) inducer runs, no spark/click and no flame at all; (b) burners light, run a few seconds, then go out; (c) only the first burner lights. Story (b) is the flame-sense branch, (a) is igniter or gas, (c) is carry-over — that single observation is most of the diagnosis.
3. Read the display properly: a steady-cycling '11' means attempts are still in progress; '11' alternating with '10' means four consecutive failures have already put the furnace in its one-hour lockout. Count attempts if you can — Rheem retries after a 20-second postpurge, up to four.
4. Confirm the simple fuel facts without opening anything: the manual switch on the gas valve is ON, the manual shut-off valve is open, and other gas appliances in the house work. A gas valve left off after unrelated plumbing work is Rheem's own second-listed cause.
5. Ask what changed: recent electrical work (polarity/ground branch), a recent control or igniter change (connections and spark position), or the first cold night after the gas was off all summer (supply branch). Code 11 usually begins at a change, not at random.
6. On an EcoNet/communicating system, check the thermostat's active-fault screen: Rheem logs 11 there from the first failure of a heat call even when the homeowner display does not show it yet — that tells you whether tonight is failure one or failure four.

How to fix rheem error code 11?

1. Owner step, once only: with the gas confirmed on and no gas smell, cycle power to the furnace off and back on and let it make ONE full set of attempts. A furnace that lights and holds has cleared a transient; a furnace that returns to 11 has given you its answer — do not keep power-cycling it into repeated lockouts.
2. Flame-sense branch (burners light, then drop out): the flame sense rod is cleaned or replaced and every connection and wire between the rod and the control checked, with the furnace ground verified. Rheem's maintenance instructions assign flame-sensor cleaning to a qualified installer, service agency or the gas supplier — treat rod work as technician work, not a Saturday chore.
3. Gas branch: turn the valve on if it was off; if the valve is on and other appliances have gas, the remaining checks — manifold pressure measured during ignition (approx. 3.5 in. w.c. natural gas, approx. 10 in. w.c. LP per the (-)97V manual) and orifice/flow restrictions — are manometer work for a licensed technician.
4. Igniter branch: check all connections and wiring between the igniter and the control, verify the igniter's placement/spark location, and replace or reposition the igniter as found — burner-compartment work, technician territory for most owners.
5. Carry-over branch: if the first burner lights and the rest do not with manifold pressure proven good, Rheem's stated cure is burner replacement — the cross-over path is damaged or blocked beyond cleaning.
6. Control branch: only after rod, gas, igniter, polarity and carry-over are proven does Rheem's list reach the furnace control itself — replace the I.F.C. (on communicating models the model data card must be saved from the old control and fitted to the new one, or the furnace trades an 11 for a d1).

The part that usually fails: Usually the flame sense rod — cleaned, reconnected or replaced (before any igniter or control is bought)

Rheem lists the rod first among code 11's causes for a reason: it is the cheapest part in the chain and the one whose failure imitates all the others. Igniter second, burner third, control last — and only on proof.

How to reset rheem furnace error code 11?

A single failed ignition needs no reset: the control postpurges for 20 seconds and retries on its own. After four consecutive failures the furnace is in the one-hour lockout (10 and 11 alternating): it auto-resets after one hour, or — once the cause is fixed — clears immediately by cycling power off and back on, or (soft lockout only) by cycling the heat call off for more than 2 seconds but less than 20 seconds. Resetting without fixing the cause just buys four more failed attempts and another lockout.

Rheem fault codes are shown as two-digit codes on the control's 7-segment display and clear once the fault condition is gone. Lockouts follow Rheem's documented rules: soft lockouts (the one-hour lockout, code 10, and the five-minute lockout when the low pressure switch fails to close after 60 seconds of inducer operation) auto-reset when their timer expires, and any lockout can be cleared immediately — once the original fault is cleared — by cycling power to the unit off and back on, or, for soft lockouts only, by cycling the heat call off for more than 2 seconds but less than 20 seconds. Hard lockouts are the exception: code 93 cannot be reset by cycling the heat call, and a dead-blower hard lockout (code 61, declared four times in one heat call) needs the repair plus a manual reset of power. Clearing a lockout without fixing its cause just restarts the count to the next one.

Why does rheem furnace error code 11 keep coming back?

An 11 that returns after the rod is cleaned and the gas proven is climbing Rheem's own cause list in order: igniter spark position degrading, carry-over worsening as burners corrode, manifold pressure sagging (a supply/regulator story that often appears only on the coldest nights when every appliance runs), or polarity/ground problems after electrical work. An 11 that arrives only on the first call after long idle periods, then runs for weeks, fits a supply or sticky-valve pattern — describe that timing to the technician; it is worth more than the code.

How to stop 11 coming back

• Flame sense rod unable to sense flame (Rheem's #1 listed cause): The rod may need cleaning or may not be properly connected. The burner can light perfectly and still produce an 11 if the rod is coated, mispositioned or its wiring to the control is open — the control never receives proof of flame inside its trial window, so it shuts the gas valve and records a failed ignition.
• Gas valve turned off / no gas to burn: Rheem's second listed cause is the gas valve being turned off. The manual switch on the gas valve left off after other work, a closed manual shut-off, or an interrupted supply all produce a textbook 11: inducer runs, igniter works, nothing lights because there is no fuel.
• Igniter not working properly: The igniter may not be properly connected, or the spark location may not be correct — on these Rheem controls ignition is by spark, and a spark landing in the wrong place lights nothing. A cracked or displaced igniter shows as an 11 with a healthy gas supply.

Retrieving stored fault codes on Rheem furnaces

Generation decides the diagnostic path. On the single-display controls (R95P, (-)801S/(-)801P) a two-digit fault is shown one digit at a time — first digit for one second, second digit for one second, then a half-second pause — repeating until the fault clears, and each fault is shown a minimum of two times. Those boards also recall history for free: on a power reset, the three most recent faults less than a week old are flashed in succession, most recent first; the fault buffer clears itself after one week and can be cleared manually with the SW4 dipswitch sequence in the manual. Communicating models (dual 7-segment display, (-)802V/(-)97V, R96V) add a pushbutton status menu on the control that steps through active faults, firing rate, airflow and the fault history (FL) — up to six faults stored within 168 powered hours — and the buffer is cleared by holding the pushbutton for 5 seconds or more while FL is active. On EcoNet systems the same faults also appear as text and alert codes at the thermostat.

Other Rheem furnace error codes

See the full list on the Rheem Furnace error codes hub.

Codes 11 gets confused with

61 — Blower fault — blower unable to run. Critical: no operation in any mode. Rheem also declares 61 when the main limit has been open over 150 seconds during a heat call (the display then alternates 61 and 22): the control reads a limit that cannot re-close as a dead blower, because the blower should be carrying the heat away. A fourth dead-blower declaration in one heat call enters hard lockout. Code 61 is Rheem's verdict that the circulating blower — the motor that moves house air over the heat exchanger and through the ducts — cannot run, and it is one of the few Rheem codes that stops everything: the SHORT chart's wording is 'no operation in any mode', so cooling and continuous-fan calls are refused alongside heating.

Frequently asked questions

Related guides

Facts on this page were checked against manufacturer documentation: pts.myrheem.com · www.manualslib.com · pts.myrheem.com · pts.myrheem.com · www.manualslib.com · my.ruud.com:443