The short answer
A Rheem furnace in Northern Virginia shows its fault one of three ways, depending on the age of the control board: a red light that blinks, a green light that blinks, or a two-digit display. The same blink count means different things on each board, so find out which one you have first. On the two-digit boards, the codes we see most are 11 (the burners didn’t light), 13 (the flame lit and went out), 22 (the furnace overheated, almost always from low airflow) and 45 (the pressure switch didn’t close, which points at the vent). On a high-efficiency furnace, 59 means a plugged condensate drain.
Which board do you have?
Look through the little window in the lower door. A red light beside a yellow one is the older board in Rheem’s RA 80+, RC 92+ and RL 90+ manuals. A single green light is the board in Rheem’s furnace FAQ. Two digits, like a clock radio, is a newer board: the R96V, R801T, R92T, R802V or the 98V series.
Count the light before you take the door off. Pulling the lower door presses a safety switch that cuts power to the board, and the code goes with it. Take a phone video through the window instead.
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Red and yellow lights (older boards)
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| Red light | What it means | What usually causes it |
|---|---|---|
| Steady | Power on, no fault | Normal |
| 1 blink | Limit open | Low airflow: the filter, closed vents, the blower |
| 2 blinks | Pressure switch open, inducer running | A blocked vent or drain, a split switch hose |
| 3 blinks | Pressure switch closed, inducer off | A stuck switch |
| 4 blinks | Ignition failure | Gas off, the igniter, the flame sensor, a poor ground |
| 5 blinks | Line and neutral reversed, or no ground | Wiring |
| Nonstop | False flame or a shorted gas valve relay | Call us |
The yellow FLAME light is steady when the flame is good and flashes when the flame signal is weak. A flashing yellow light usually means a dirty flame sensor, a few weeks before it turns into a no-heat night.
One green light
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| Green light | What it means | What usually causes it |
|---|---|---|
| 1 blink | Soft lockout: four failed tries to light, or four lost flames | The flame sensor, the gas supply, the igniter |
| 2 blinks | Pressure switch circuit open | A blocked vent or switch port, a weak inducer |
| 3 blinks | Limit circuit open | Low airflow, or the rollout switch over the burners tripped |
| 4 blinks | Pressure switch closed while off | A stuck switch |
| 5 blinks | Twinning fault | Two furnaces wired to run as one |
Rheem says a 1-blink soft lockout clears if you cut power, or turn the thermostat off, for 5 to 10 seconds. Our Rheem reset guide covers when that’s safe.
The two-digit display
The display shows the first digit for a second, then the second digit, then pauses for half a second and starts over. So 4, then 5, then a pause is code 45, not two codes. Every fault flashes at least twice, even if it already cleared. A letter isn’t a fault: 0 is standby, H is heat (a small h is low heat on a two-stage furnace), C is cooling, F is the fan alone and CL means the board is calibrating the inducer.
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| Code | What it means | What usually causes it |
|---|---|---|
| 10 | One-hour lockout | Alternates with the real code |
| 11 | Failed ignition | Gas valve off, the igniter, the flame sensor |
| 12 | Low flame sense | A dirty or loose flame sensor |
| 13 | Flame lost after it lit | The flame sensor or an unsteady flame |
| 14 | Flame with the gas valve off | Rare and serious: call us |
| 22 | Main limit open | Low airflow: the filter, closed vents, the blower |
| 26 | Line and neutral reversed, or a poor ground | Wiring |
| 30 | Open fuse | A short on the thermostat or outdoor wiring |
| 33 | Rollout switch open | A venting or flame problem |
| 44 / 55 | Pressure switch closed, inducer off | A stuck switch |
| 45 / 46 / 57 | Pressure switch open, inducer running | A blocked or too-long vent, the inducer, split hoses, wind |
| 58 / 59 | Water sensor open / water sensed | A loose sensor wire / a plugged condensate drain |
| 60 / 61 | Blower maxed out / blower can’t run | The ducts or filter / the motor |
| 66 | Blower cutback | Not a fault: restricted airflow |
| 93 | Internal control fault | The board needs replacing |
| d1 / d4 / d6 | Memory card problem | Missing or wrong card after a board swap |
That’s the R96V list; the R802V and the 98V series read the same. On an R801T or R92T, a pressure switch problem shows as 55, 56 or 57 instead of 45. A code that isn’t on the list may just be the display reading upside down: a dip switch on the board flips it.
Lockouts
The two-digit boards lock out in steps. If the pressure switch doesn’t close within a minute, the furnace waits five minutes and retries. After four failed ignitions, five lost flames or a blower that won’t run, it locks out for an hour and alternates 10 with the cause, so 10, 11, 10, 11 means it gave up on lighting. Code 93 waits for a technician.
What you can safely check
- Count the code through the window and take a video.
- Change the filter if it’s gray. A clogged one is behind most 22s and 66s. Our filter guide covers sizes.
- Open the supply vents and clear the return grilles.
- Outside, clear leaves, snow or a nest from the white PVC pipe ends without pushing anything in.
- On a high-efficiency furnace, check the condensate pump. A full pump goes with 59 and the pressure switch codes; our condensate drain guide walks through it.
- Reset once: furnace switch off for 30 seconds, then back on.
What not to do
Never jump or bypass a safety switch to get heat back. Each one is there to stop the furnace from burning gas when something is wrong, and the wrong thing is often exhaust, which carries carbon monoxide. Don’t reset a rollout switch (33) and keep running the furnace: it trips because flame came out of the burner box. If your carbon monoxide alarm goes off, get everyone outside first and read our CO alarm guide from there. If you smell gas, don’t flip any switches: leave the house and call your gas company or 911 from outside.
What a technician does
We read the fault history first. An R96V keeps its last six faults for about a week; an R801T or R92T flashes its last three each time the power comes back. Then we test what the code points at: microamps at the flame sensor, a manometer on the pressure switch, gas pressure at the valve (about 3.5 inches of water column on natural gas), the temperature rise and the duct static. You get the price before we fix anything.
Our heating check is $67 per system, through December 31: furnace, heat pump or boiler.
Related: Ruud furnace codes, Rheem furnace not igniting, flame sensor problems, every brand in our error codes guide and our Rheem page.
Every code meaning here comes from Rheem’s own documents: R96V manual, R801T manual, R92T manual, R802V manual, RA 80+ manual, RC 92+ and RL 90+ manual and furnace FAQ.
Call or book
A repair visit starts with a flat $99 diagnostic, or $250 after hours, and you get the price of the fix before we touch anything. Call (703) 997-9757, day or night, and tell us the code you counted, or book online from goswiftpro.com/cookiesoffer by November 30 and a box of warm MOLTN cookies comes with the heating check. Every current deal is on our offers page. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
What does a blinking red light on a Rheem furnace mean?
On the older boards with a red and a yellow light, the red count is the code: 1 is the limit (usually airflow), 2 is the pressure switch open, 3 is the pressure switch stuck closed, 4 is ignition failure and 5 is reversed wiring or no ground. Steady red is normal.
What does code 45 mean on a Rheem furnace?
The low pressure switch didn’t close with the inducer on high. Start with the vent pipes outside and the condensate drain, then the inducer, its hoses and the switch.
What does 10 and 11 alternating mean on a Rheem furnace?
It locked out for an hour after four failed tries to light. 10 is the lockout and 11 is the reason. It clears itself after an hour, but find out why it didn’t light first.
How do I clear the codes on a Rheem furnace?
On an R96V, hold the button on the board 5 seconds or more in the FL menu. On an R801T or R92T, flip dip switch SW4 on and off three times within 30 seconds. Write the codes down first: clearing them fixes nothing.
