Carrier · Status code
Carrier 59SC6A status code 23: pressure switch stuck closed
Major code 23 means the control found a pressure switch already closed before the inducer started, when the switch should be open. Minor 23.1 is the main pressure switch stuck closed; minor 23.2 is the secondary pressure switch stuck closed.
On the control
- Code
- 23
- Minor
- 23.1 · 23.2
- Door LED
- 2 short flashes then 3 long
- Controller
- 59SC6A integrated furnace control with 3-digit LCD display and door LED
- Applies to
- Carrier Comfort 96 (59SC6A)
- Manual
- 59SC6A-01SI REV D
What each minor code says, verbatim
| Display | Manufacturer wording |
|---|---|
| 23.1 | Stuck closed Main pressure switch |
| 23.2 | Stuck closed secondary pressure switch |
A code is a condition, not a diagnosis
A switch reported stuck closed can be the switch itself, but more often it is the sensing line: a disconnected or cracked hose, a blocked port holding the switch closed, or water in the line. The switch is tested with a manometer against its printed set-point.
Which furnaces this applies to
Documented for Carrier 59SC6A Comfort 96 furnaces in installation instructions 59SC6A-01SI REV D. The control checks that the switch contacts are open before starting the inducer, so a switch that fails closed or a sensing line that is off or blocked sets this code.
Scope: Carrier 59SC6A Comfort 96 furnaces with the on-board 3-digit display control. Not sure which control you have? Send us the full model number from the rating plate.
Safe things to look at first
- Read the full code on the control display through the door, including any minor digit (for example 33.2), and write it down.
- Look, without touching, for obvious conditions you can report: snow or ice at the vent terminations, water on the floor, a loaded filter, a condensate pump that is full or off.
- Note whether the furnace still heats at all, and how long it runs before the code returns.
- Note whether the furnace runs at all and whether the code appears at power-up or after a cycle.
Do not
- Do not bypass or jumper the door switch, limit switches, rollout switches or pressure switches.
- Do not open the burner compartment, disconnect tubing, or adjust the gas valve or gas pressure.
- Do not keep cycling power to force the furnace to relight; repeated resets hide the fault and can allow unburned gas to build up after ignition failures. If the code returns, stop and call.
What a technician does
- A technician checks the switch contacts with power off, inspects the hoses and ports, verifies the switch opens at its printed break point with a manometer, and checks the condensate path before replacing anything.
Same code, other equipment
- Carrier 59TP6C two-stage controls: The two-stage Performance 96 prints the same major 23 with sub-codes 23.4 and 23.5 (LPS and HPS stuck closed). Sub-code numbers differ between stages; read the label on your furnace.
Related components and symptoms
Questions people ask
What does a stuck-closed pressure switch mean for my furnace?
The control refuses to start the burner because a switch that should be open is closed, which could let the control misread the draft condition. It is a safety check doing its job; the cause is found by testing the switch and its tubing.
Seeing code 23 on your Carrier?
Tell us the full code, the model number and whether the furnace still heats on low. BC Wide prioritizes no-heat calls across Greater Vancouver.