Next Phase Heating is an independent HVAC contractor. We are not an authorized dealer for, or affiliated with, any equipment manufacturer. Brand names are used only to identify the equipment we service. Codes vary by model and model year — the legend on your own furnace is always the last word.
First — what you are actually looking at
Rheem states in its own installation instructions that all its furnace controls come standard with a seven-segment diagnostic display. If yours is blinking a count at you, you have an older board than this page covers.
One digit, then the next, then a pause
Most models have a single character display, so a two-digit code arrives in sequence: the first digit for a second, the second digit for a second, then a short pause before it repeats. It is not two separate codes.
Or both digits at once
The modulating and higher-end models have a two-character display and show the whole code together. Easier to read, same code list.
Letters are not faults
A zero on its own means standby and nothing is wrong. C means it is running for cooling or the heat pump, H means gas heat, F means the fan is running continuously. All four get reported as error codes regularly.
The legend really is on the door
Rheem is the one brand here that states plainly in its literature that the troubleshooting flowchart is printed on the inside of the blower door. Yours is the definitive version for your furnace.
What the numbers mean
Stop, and call someone
Two codes, both about flame going somewhere it should not.
33
The manual reset limit has opened — this is the rollout switch
Rheem calls it the MRLC, and the important word in that name is manual. It does not reset itself and it is not supposed to. It has opened because heat or flame reached somewhere it should never reach. Shut the furnace off at the service switch and leave it off.
14
A flame is being detected when there should not be one
The control can see flame with the gas valve closed. Switch it off. If you can smell gas at all, leave the house and call the gas company first.
Worth ten minutes before you book
The pressure switch codes on a Rheem are unusually specific, which is genuinely helpful — they tell you which switch and at what inducer speed.
22
The main limit has opened — the furnace overheated inside the cabinet
Filter, registers, return, in that order. Some revisions of the Rheem manual word this code as the main limit or the high altitude limit control, so on a unit that has been set up for altitude it can mean something slightly different.
57
The high pressure switch is open when it should be closed
This is the venting one. On a high-efficiency furnace go outside and look at the white plastic intake and exhaust pipes: nests, snow, and anything blown over the ends all cause exactly this.
45 · 46
The low pressure switch is open, with the inducer running high or low
Same outdoor check as 57. The two codes differ only by which inducer speed was running at the time, which helps a technician a great deal and does not change what you can check yourself.
59
Water has been sensed where it should not be
The condensate drain has backed up. Very common in the first properly cold week, when a line that sat dry all summer turns out to be blocked.
Needs a technician, but it is not an emergency
Rheem grades some of these itself. Where it calls something a critical fault, we have said so.
10
One hour lockout after repeated ignition retries
The furnace has stopped trying and will have another go in an hour. Once is a bad morning. Twice is a fault.
11
Failed ignition
It called for heat and never lit. Igniter, gas supply or flame sensing.
12
Low flame sense
A flame sensor with a film of oxide on it, nine times out of ten. Small part, quick visit, extremely common.
13
The flame was established and then lost
Different from 11 and it points somewhere different — often gas pressure or the flame sensor rather than the igniter.
55
The high pressure switch is closed when it should be open
The opposite of 57. Usually a switch that has stuck rather than anything to do with venting.
44
The low pressure switch is closed when it should be open
Same idea, the other switch.
20
Twinning fault
Only applies where two furnaces are wired to run as a pair, which is unusual in a house.
26
Line and neutral are reversed
A wiring fault rather than a furnace fault. Turns up most often after other work has been done.
58
The water sensing circuit is open
Usually the sensor jumper rather than actual water. Different from 59, which means water was genuinely detected.
61
The blower cannot run
Motor or module. On the variable speed units this is the more common of the two blower codes.
93
Internal control fault
The board has found a problem with itself.
Four ways a Rheem code gets read wrong
- Most Rheem troubleshooting articles online are for the wrong system. There is a lot of content describing Rheem status light blink counts. Those describe older multi-LED boards. Rheem states that its current furnace controls all ship with a seven-segment display, and the code numbers on this page do not translate into blink counts.
- One digit at a time reads like two codes. On a single-character display, 57 arrives as a 5, then a 7, then a pause. People report it as code 5 and code 7, or write down whichever they happened to catch.
- The display is not always the right way up. Rheem’s own instructions refer to display segments being turned vertical in some installations. Depending on how your furnace sits, digits can be read sideways or upside down — and a rotated display is how a 2 becomes something else entirely.
- Zero is the healthy state. Standby. Nothing wrong. It is reported as an error more than any other reading on the display.
There is no error code for a cracked heat exchanger
People search for this constantly, so here is the straight answer: no Rheem or Ruud control board detects a cracked heat exchanger, and no other manufacturer’s does either. There is no code and there never has been. A board can tell you the manual reset limit opened, or that the main limit keeps tripping, and both can be downstream signs of an exchanger that has failed. But the crack itself is found by inspection — someone with a camera and a combustion analyser, taking the thing apart. If a quote for a whole new furnace arrives on the strength of a number on a display, that is worth a second opinion before you spend anything.
Read the number off the display?
Book the visit and put it in the notes. On a Rheem the code is specific enough that it usually tells us which part to bring.
Book a Furnace Diagnostic60 seconds online · or call (206) 486-6373
How it works when you book
- 1
Read the code before you reset anything The moment you cycle the power the live code is gone. Count it twice and write it down.
- 2
Book online and tell us what it showed Takes about a minute. Put the code in the notes — it changes what the technician loads into the van.
- 3
You get the price before we start Diagnosed, explained, and quoted in writing. Nothing happens until you say go.
Our service areas
We run out of Covington and cover the greater Puget Sound area.
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Snohomish County
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Not on the list? We cover the greater Puget Sound area around our Covington base. Book it and a technician confirms within 1 business hour.
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Quick answers
Is a Ruud furnace the same as a Rheem?
Same manufacturer, same control boards, same codes. Everything here applies to both.
My furnace blinks rather than showing a number. Is this page wrong for me?
It means you have an older board than this covers. Rheem did use a multi-LED blink system before the digital display. We would rather tell you that than have you match your blink count to a number on this page, because they do not correspond.
It says H and the house is cold. Is H a fault?
No, H means the furnace is in gas heat mode. If it is showing H and the house is not warming up, the furnace thinks it is heating, which points at airflow, a stuck blower or a duct problem rather than the burner. Worth a look.
How do I clear a code once it is fixed?
It depends on the model, which is a good reason not to follow a generic instruction. Some Rheem boards have a fault recall button you hold for three seconds. Others want a specific dip switch sequence within thirty seconds. The literature for your model number has the right one.
Do you work on Rheem if we bought it elsewhere?
Yes. Rheem asks that work is done by a qualified, trained HVAC professional to the applicable codes. It does not ask you to use a particular dealer, so nothing about using us affects your parts warranty.
Give us the number and we will bring the part.
Book online in about a minute. Put the two digits in the notes, and say whether they appeared together or one after the other.
Book a Furnace Diagnostic60 seconds online · or call (206) 486-6373
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