Payne PG96VTA Error Code 31: High-Heat Pressure Switch or HPSR Relay Did Not Close or Reopened
What Does Code 31 Mean?
Code 31 (three short flashes followed by one long flash) flags the high-heat pressure switch input. On this two-stage furnace there are separate pressure switches for the low-heat and high-heat firing rates. When the control calls for high heat, it expects the high-heat pressure switch to close, proving the inducer is moving enough combustion air for the higher firing rate.
The code sets when that switch fails to close on a high-heat call, or opens during high-heat operation. The manual also implicates the HPSR (high-heat pressure switch relay) on the control board, which switches this input. So the fault can be the switch, the relay, or the draft itself — for example a blocked or restricted vent that keeps the inducer from generating enough pressure at high fire.
Code 31 is part of the same pressure-switch family as code 32 (low-heat pressure switch did not close) and code 43 (low-heat switch open while high-heat switch closed); the manual explicitly cross-references code 32. Because it involves the pressure switch, the board relay, and the venting system, it is diagnosed by a technician.
What You'll Notice
- The furnace runs on low heat but will not step up, or drops out when it tries to go to high heat
- The amber LED flashes three short flashes followed by one long flash (code 31)
- Heat output seems weak on the coldest days, when the furnace should be at high fire
- The burners may light and then shut down shortly after attempting high-heat operation
- The problem can track with vent blockage, high wind, or a failing inducer
Common Causes
How This Is Diagnosed
A technician confirms the inducer is developing adequate draft, inspects the vent and intake piping for restriction, and measures the high-heat pressure switch to see whether it closes at the correct pressure. They also check the HPSR relay on the control board that switches this input.
Because this spans the pressure switch, the control-board relay, the inducer, and the venting system, it is professional work. A homeowner can note whether the problem coincides with high winds or an obviously blocked outdoor vent termination, but the diagnosis itself is not DIY.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace only runs on low heat and will not step up to high heat
- The furnace drops out or shows code 31 whenever it tries to reach high fire
- Heat is weak during the coldest weather, when high-heat operation is expected
- The outdoor vent or intake termination is blocked, or the code worsens in high wind
Frequently Asked Questions
What does code 31 mean on a Payne PG96VTA?
It means the high-heat pressure switch did not close when the furnace called for high heat, or it reopened during high heat. Causes include weak inducer draft, a blocked vent, a faulty switch, or a defective HPSR relay on the board.
Why does my furnace only run on low heat now?
If the high-heat pressure switch will not prove, the control keeps the furnace from going to high fire and flags code 31. A technician needs to check the switch, the venting, and the board's HPSR relay.
What is the HPSR relay?
The HPSR (high-heat pressure switch relay) is a relay on the control board that switches the high-heat pressure switch input. If it is defective, the control cannot verify high-heat draft and sets code 31.
✓ Verified against manufacturer service manual — March 2026