Carrier · Status code
Carrier 59SP6B status code 31: secondary pressure switch open or lockout
Major code 31 covers the secondary pressure switch (HPS) on the Performance 96 single-stage. Minor 31.2 means the switch is open when the control expects it closed; minor 31.3 means the switch failed to close during three consecutive trials and the control locked out.
On the control
- Code
- 31
- Minor
- 31.2 · 31.3
- Door LED
- 3 short flashes then 1 long
- Controller
- 59SP6B integrated furnace control with 3-digit LCD display and door LED
- Applies to
- Carrier Performance 96 single-stage (59SP6B)
- Manual
- 59SP6B-01SI REV B
What each minor code says, verbatim
| Display | Manufacturer wording |
|---|---|
| 31.2 | Open secondary pressure switch (HPS) |
| 31.3 | Secondary PS Lockout - failed to close secondary PS after three trials |
A code is a condition, not a diagnosis
A secondary switch that will not close points at the draft side: a blocked or frozen vent or intake, a flooded condensate trap or drain, a cracked or disconnected hose, an inducer not reaching speed, or the switch itself. A manometer reading against the switch's printed set-point distinguishes these.
Which furnaces this applies to
Documented for Carrier 59SP6B Performance 96 single-stage furnaces in installation instructions 59SP6B-01SI REV D. The pressure switches carry reference labels and nominal break points printed on the switch.
Scope: Carrier 59SP6B Performance 96 single-stage 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.
- Check the vent and intake terminations for snow, ice, leaves or a nest, and the floor around the furnace for water. Note whether the inducer runs when the thermostat calls.
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 measures the pressure at the switch with a manometer, checks the inducer, inspects the condensate trap and drain, and tests the switch against its label set-point before replacing it.
Same code, other equipment
- Carrier 59TP6C two-stage controls: The two-stage Performance 96 prints the same major 31 with sub-codes 31.6 and 31.7 for its high-heat switch. Sub-code numbers differ; read the label on your furnace.
Related components and symptoms
Questions people ask
What is the difference between codes 31 and 32 on the Performance 96 single-stage?
31 covers the secondary pressure switch (HPS); 32 covers the main pressure switch. Both prove draft, but through different switches and hose paths.
Why does code 31.3 appear after several attempts?
31.3 means the switch did not close in three trials, so the control locked out instead of cycling forever. The underlying draft or condensate cause still needs to be found.
Seeing code 31 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.