What It Means
High-heat pressure switch failed to close or opened during high heat.
Carrier Furnace
Carrier Furnace Error Code 31
Troubleshooting guide for the Carrier Furnace system fault 31.
Possible Causes
- Inducer motor speed loss or failure.
- Blocked pressure switch tubing or condensate trap.
- Faulty high-heat pressure switch.
- Restricted flue pipe or vent termination.
Not sure which one it is — or if it's none of these? Try ACLogics today.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis
High-Heat Pressure Switch or Relay Did Not Close or Reopened. High-heat pressure switch input failed to close on a call for high heat, or opened during high heat.
All Recorded Causes
Check inducer motor speed and operation. Inspect pressure switch tubing for blockage or leaks. Test high-heat pressure switch with manometer. Verify vent system is clear and properly sized.
Verify Before Replacing Parts
- Confirm the exact Carrier model family and furnaces context before acting on a generic code description.
- Walk the entire heating sequence in order instead of jumping straight to the reported code, watching for check inducer motor speed and operation.
- Verify each safety device and prove where the sequence stops under live operation, including whether inspect pressure switch tubing for blockage or leaks.
- After the correction, run the system long enough to confirm the furnaces fault does not return under normal load.
Still unsure about this fault?
ACLogics walks you through Carrier Furnace diagnostics step-by-step — so you confirm the cause before swapping parts.
