Carrier 58MVP Error Code 31: High-Heat Pressure Switch or Relay Did Not Close or Reopened
What Does Code 31 Mean?
Status code 31 on the Carrier 58MVP indicates that the high-heat pressure switch input failed to close on a call for high-heat, or opened during high-heat operation. The pressure switch is a safety device that confirms the inducer motor is generating enough draft to safely vent combustion gases.
When the furnace calls for high-heat, the inducer motor runs at high speed and creates negative pressure in the heat exchanger and vent system. The high-heat pressure switch monitors this pressure. If the switch does not close (indicating insufficient draft) or reopens during operation, the furnace shuts down to prevent exhaust gases from entering your home.
The most common cause is a blocked or restricted exhaust vent. Snow, ice, leaves, bird nests, or insect nests can block the vent pipes where they exit your home. This code is related to code 32 (low-heat pressure switch), which affects low-heat operation.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Blocked or restricted exhaust vent | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The exhaust vent and intake appear clear but code 31 persists
- The inducer motor sounds unusually loud, weak, or does not start
- Ice keeps forming at the vent termination despite clearing it
- Code 31 occurs primarily on windy days (may indicate improper vent termination)
- You suspect the control relay or gas valve wiring may be at fault
✓ Verified against manufacturer service manual — March 2026