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- Code 14.4
Carrier gas furnace code 14.4: Lockout after repeated pressure switch openings
Gas furnace, Canada and United States
The control locked out heating after the pressure switch opened 7 times in one heat request. The 59TP6C-series labels say LPS open events, while the 59TN7A label says pressure switch open events.
This needs a licensed gas technician. There are a few safe checks you can do first, marked below. Anything inside the unit is a job for a professional.
This involves the flue or exhaust. A blocked or leaking flue can let carbon monoxide into the home.
Only some models show this code. Check the list below.
What causes it
InteliSense display furnaces
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A restricted or wrongly sized vent, or strong wind at the vent.
Check the vent and air intake pipes outside are clearYou can do this
- Find where the furnace vent pipe ends outside the house. A two-pipe (direct-vent) installation also has an air intake pipe ending outside. Check only what you can see from the ground. Do not climb onto the roof or use a ladder. If the vent ends on the roof or goes into a chimney, book a technician to check it.
- Check nothing is blocking or covering the ends of the pipes, in any season, and clear anything stored or growing around them.
- On a condensing furnace with a one-pipe installation, also check the combustion-air pipe next to the furnace is not blocked and nothing is crowding the air openings around the furnace.
- If a pipe is blocked inside, has holes or has come apart, do not run the furnace. Call your dealer. A blocked, holed or disconnected vent pipe can let toxic fumes into your home.
- Find where the furnace vent pipe ends outside the house. A two-pipe (direct-vent) installation also has an air intake pipe ending outside.
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Disconnected or blocked pressure tubing, or a faulty pressure switch.
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On condensing furnaces, a plugged condensate drain or water lying in a sagging vent pipe.
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Not enough combustion air.
InteliSense ultra-low NOx furnaces
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A restricted or wrongly sized vent, or strong wind at the vent.
Same check as above: Check the vent and air intake pipes outside are clear
-
Disconnected or blocked pressure tubing, or a faulty pressure transducer.
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A failed inducer motor, or low voltage to the inducer.
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On 59CU5B, a restricted or blocked condensate drain.
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Not enough combustion air.
InteliSense modulating furnaces
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A restricted or wrongly sized vent, or strong wind at the vent.
Same check as above: Check the vent and air intake pipes outside are clear
-
Disconnected or blocked pressure tubing, or a faulty pressure switch.
-
A plugged condensate drain or water lying in a sagging vent pipe.
-
Not enough combustion air.
-
Low or fluctuating gas inlet pressure, or manifold pressure or firing rate set wrongly.
How to read this code on your unit
The three-digit display sits on the furnace control behind the blower door. Through the sight glass in the door you see only the status light, which flashes the first two digits of the code. Count the short flashes for the first digit, then the long flashes for the second, so 3 short flashes followed by 3 long flashes is a 33.x code. Write down what you see before you open the door or switch the furnace off. The full code with its third digit shows on the control display only with the door removed and the door switch closed, which is a job for a technician. A technician can also look back at the last 7 faults in the FLt menu. Stored codes are erased by themselves after 72 hours of powered operation after the last fault, and the display shows non when no fault is stored.
Booking a licensed gas technician
Book a licensed gas technicianlicensed gas technician
- Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
- Note the code, how often it appears, and the model and serial numbers from the rating label.
- Book a licensed gas technician and give them those details.
Models that show this code
56 models in 9 ranges
| Range | Models |
|---|---|
| 58TP0B/58TP1B | 58TP0B045V14-12, 58TP0B070V14-12, 58TP0B070V17-16, 58TP0B090V17-16, 58TP0B090V21-20, 58TP0B110V21-22, 58TP0B135V24-22, 58TP1B045V14-12, 58TP1B070V14-12, 58TP1B070V17-16, 58TP1B090V17-16, 58TP1B090V21-20, 58TP1B110V21-22, 58TP1B135V24-22 |
| 59TN7A | 59TN7A060C17-16, 59TN7A080C17-16, 59TN7A080C21-20, 59TN7A100C21-22, 59TN7A120C24-22 |
| 59TP6C | 59TP6C040V14-10, 59TP6C040V17-12, 59TP6C060V14-12, 59TP6C060V17-16, 59TP6C080V17-16, 59TP6C080V21-20, 59TP6C100V21-20, 59TP6C100V21-22, 59TP6C120V24-22 |
| 59TP7A | 59TP7A060V17-16, 59TP7A080V17-16, 59TP7A080V21-20, 59TP7A100V21-20, 59TP7A100V21-22, 59TP7A120V24-22 |
| 58CU0B | 58CU0B040C17-12, 58CU0B060C17-16, 58CU0B080C21-20, 58CU0B100C21-20 |
| 58SU0B | 58SU0B040M17-12, 58SU0B060M17-16, 58SU0B080M21-20, 58SU0B100M21-20 |
| 59CU5B | 59CU5B060C17-16, 59CU5B080C21-20, 59CU5B100C21-22 |
| 59SU5B | 59SU5B040M17-12, 59SU5B060M17-16, 59SU5B080M21-20, 59SU5B100M21-20, 59SU5B100M21-22 |
| 59MN7C | 59MN7C060C17-14, 59MN7C060C21-20, 59MN7C080C17-14, 59MN7C080C21-20, 59MN7C100C21-22, 59MN7C120C24-22 |
Where this comes from
- 59TP6C gas furnace, installation, start-up, operating and service instructions (59TP6C-03SI) , page 56, 76
- 59TN7A gas furnace, installation, start-up, operating and service instructions (59TN7A-04SI) , page 55, 74
- 58TP0B gas furnace, installation, start-up, operating and service instructions (58TP0B-01SI) , page 49
- 58SU0B gas furnace, installation, start-up, operating and service instructions (58SU0B-03SI) , page 24, 39
- 59SU5B gas furnace, installation, start-up, operating and service instructions (59SU5B-03SI) , page 48
- 58CU0B gas furnace, installation, start-up, operating and service instructions (58CU0B-03SI) , page 28, 43
- 59CU5B gas furnace, installation, start-up, operating and service instructions (59CU5B-05SI) , page 49, 66
- 59MN7C gas furnace, installation, start-up, operating and service instructions (59MN7C-04SI) , page 53, 74
- 59TN7A gas furnace, installation, start-up, operating and service instructions (59TN7A-04SI) , page 74
Checked against the manufacturer's manual on 11 October 2026.
Other Carrier gas furnace codes
| Code | Meaning | What you can do |
|---|---|---|
| 23 | Flue or venting fault (depends on model) | Call a pro |
| 31 | Flue or venting fault (depends on model) | Safe checks first, then a pro |
| 32 | Low or low-heat pressure switch did not close, or opened again | Safe checks first, then a pro |
| 42 | Inducer motor fault | Safe checks first, then a pro |
| 43 | Lower pressure switch open while a higher one is closed | Call a pro |
| 23.1 | Flue or venting fault (depends on model) | Call a pro |
| 23.2 | Secondary pressure switch stuck closed | Call a pro |
| 23.3 | Pressure transducer senses over-pressure | Call a pro |
| 23.4 | Low pressure switch stuck closed | Call a pro |
| 23.5 | High pressure switch stuck closed | Call a pro |
| 23.6 | Medium pressure switch stuck closed | Call a pro |
| 31.1 | Flue or venting fault (depends on model) | Depends on your model |
See all flue or venting fault codes on gas furnaces across brands.