Carrier 59SC2B Error Code 23: Pressure Switch Did Not Open
What Does Code 23 Mean?
Status code 23 on the Carrier 59SC2B indicates that the pressure switch failed to open when the control board expected it to. The pressure switch is a safety device that should be normally open and only close when the inducer motor creates sufficient draft for safe combustion. After the inducer shuts off, the switch should return to its open state.
When the switch stays closed inappropriately, it usually means one of two things: the pressure tubing connected to the switch is obstructed (keeping pressure applied to the switch diaphragm), or the switch contacts themselves are mechanically stuck in the closed position. Obstructions in the tubing can come from condensation, insects, or debris.
A technician will need to disconnect the pressure tubing and check for blockages, then test the pressure switch with a manometer to verify it opens and closes at the correct pressure thresholds. If the switch contacts are stuck, the pressure switch needs to be replaced.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Obstructed pressure tubing | Common | ✗ Call a pro → |
| Pressure switch stuck closed | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- When this code appears — testing and replacing pressure switches and clearing tubing obstructions requires a qualified HVAC technician
✓ Verified against manufacturer service manual — March 2026