Carrier Furnace Code 23
WarningShown as: 2 short flashes, 3 long flashes
Pressure switch did not open. The control expected the vent pressure switch to be open at the start of the cycle and it was still closed.
Manual wording: “23 PRESSURE SWITCH DID NOT OPEN - Check for: - Obstructed pressure tubing. - Pressure switch stuck closed.”
Documented for: 58SC0A, 58MCB, 58MVP, 58UVB
Likely causes, most common first
- Obstructed pressure tubing
- Pressure switch stuck closed
When to call a technician
The pressure switch is a combustion safety device. A technician needs to inspect the tubing and switch - never bypass or jumper a pressure switch.
A Carrier furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Troubleshooting Guide - Variable Speed, Two-Stage Gas Furnaces (Form 58-06T) (Carrier, 58MVP, 58UVB and other Carrier variable-speed two-stage gas furnaces (replaces 58MVP-10SM)) · checked 2026-08-25
- Installation, Start-Up, Operating and Service and Maintenance Instructions - 58SC0A/58SC1A (Carrier, 58SC0A/58SC1A single-stage 4-way multipoise condensing gas furnace) · checked 2026-08-25
- 58MCB 4-Way Multipoise Fixed-Capacity Condensing Gas Furnace - Service Manual (Carrier, 58MCB single-stage condensing gas furnace) · checked 2026-08-25