The short answer
A Ruud furnace in Northern Virginia with a two-digit display reads the same codes a Rheem does: Ruud furnaces share Rheem’s installation manuals, down to the document number. The ones we see most are 59 (water where it shouldn’t be, almost always a plugged condensate drain), 22 (the furnace overheated, usually a clogged filter), 45 (the pressure switch didn’t close, which points at the vent) and 10 alternating with another code, which means it locked out for an hour. A 0, C, H or F isn’t a fault at all.
How to read the 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. If you searched “Ruud furnace code 0” or “code H”, that’s your answer: the furnace is telling you what it’s doing, not what’s wrong.
Read it through the window in the lower door. Pulling that door presses a safety switch that cuts power to the board, and the code goes with it.
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The codes
Swipe to see all columns →
Swipe to see all columns →
| Code | What it means | What to check |
|---|---|---|
| 10 | One-hour lockout | Read the code it alternates with |
| 11 | Failed ignition | The gas valve handle, then call |
| 12 / 13 | Weak flame signal / flame lost after it lit | Usually the flame sensor |
| 14 | Flame with the gas valve off | Call us now |
| 20 | Twinning fault (on boards that use it) | Only matters with two furnaces wired as one |
| 22 | Main limit open | Filter, vents, return grilles |
| 23 | HALC limit circuit open | A missing jumper or an open limit: call |
| 26 | Line and neutral reversed, or a poor ground | Call: it’s wiring |
| 30 | Open fuse | A short in thermostat or outdoor wiring |
| 33 | Rollout switch open | Don’t reset it: call |
| 44 / 55 | Pressure switch closed, inducer off | A stuck switch |
| 45 / 46 / 57 | Pressure switch open, inducer running | Vent pipes outside, condensate drain |
| 58 | Water sensor circuit open | A loose or unplugged sensor wire |
| 59 | Water sensed | The condensate drain, trap and pump |
| 60 / 61 / 66 | Blower trouble or cutback | Filter and ducts first |
| 68 | No blower communication | Call |
| 93 | Internal control fault | The board needs replacing |
58 and 59: the water codes
A high-efficiency Ruud makes water as it burns, and a sensor in the collector box watches for water backing up. 59 means it found some: the drain, the trap or the condensate pump is plugged, and the furnace shuts down before water reaches the inducer. 58 means the sensor’s circuit is open: a loose wire, a sensor knocked out of place, or a wire touching metal. Our condensate drain guide covers clearing the line.
22: the overheating code
The main limit opens when the heat exchanger gets too hot, and that almost always means not enough air is moving across it: a clogged filter, closed vents, blocked returns, or a blower that isn’t running. If the limit stays open longer than about two and a half minutes, the board assumes the blower is dead, shows 61 and locks out.
26: the wiring code
The board checks that the hot and neutral wires are where they belong and that the furnace is grounded, because the flame sensor needs a good ground to see the flame. 26 after an electrician’s visit or a new outlet usually means the wiring got swapped. It’s a call, not a fix to try.
d1, d4 and d6: the memory card
These boards keep the furnace’s model data on a small memory card that stays with the furnace when the control is replaced. d1 means the card is missing and the furnace won’t run, d4 means its data is unreadable, and d6 means the horsepower on the card doesn’t match the blower. You’ll usually see these right after a board swap.
What you can safely check
- Write the code down or take a video through the window.
- Change the filter. Our filter guide covers sizes.
- Open the supply vents and clear the return grilles.
- Clear the PVC pipe ends outside of leaves, snow or a nest.
- Check that the condensate pump isn’t full and its hose isn’t kinked.
- Turn the gas valve handle in line with the pipe, then reset once: furnace switch off for 30 seconds, then 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 33 and keep running the furnace. 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 pull the fault history from the board first, since the code on the display may not be the one that started it. Then we test the part the code points at: the drain and water sensor for 58 and 59, static pressure and the blower for 22, 60 and 61, the vent and pressure switch with a manometer for 45, polarity and ground for 26. You get the price before we fix anything.
Our heating check is $67 per system, through December 31: furnace, heat pump or boiler.
Related: Rheem furnace codes, including the older blinking-light boards, how to reset a Rheem or Ruud furnace, furnace short cycling and every brand in our error codes guide.
Every code meaning here comes from Rheem’s own documents: Ruud U98V installation manual, R96V manual and R802V manual.
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
Are Ruud and Rheem furnace codes the same?
On the two-digit display, yes. Ruud’s 98V furnace uses the same installation manual as Rheem’s, down to the document number, and the codes read the same. If yours has a blinking light instead of digits, use the chart printed inside the furnace door.
What does code 59 mean on a Ruud furnace?
The water sensor found water backing up in the collector box. Clear the condensate drain, trap and pump. If the drain is clear and 59 comes back, the sensor or its wiring needs a look.
What does code 58 mean on a Ruud furnace?
The water sensor’s circuit is open: a loose wire, an unplugged connector or a sensor out of place. The furnace won’t run until the circuit is whole again.
What does a flashing 10 mean on a Ruud furnace?
A one-hour lockout. It alternates with the code that caused it, such as 11 for failed ignition or 13 for lost flame, and it clears itself after an hour.
