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Carrier · Furnace

23 Pressure switch did not open

Medium severity 59TP6A58SB0A/58SB1A

What the control is telling you

At the start of a heat call the control found the pressure switch already closed when it should be open.

Applies to: 59TP6A two-stage variable-speed ECM multipoise condensing gas furnace, all sizes (040-10 to 120-22)

Likely causes

  • Obstructed pressure tube
  • Pressure switch stuck closed

Test and repair steps

  1. Warning: Shut off 115-V power and gas, and lock/tag out before working inside the furnace; there may be more than one power source.
  2. Check the pressure tubing for blockage or water.
  3. Check switch continuity with the inducer off; it should be open.
  4. Replace the switch if stuck closed. Rated break tolerance is +/-0.05 in. W.C. of the nominal value on the label.
  5. Restart and confirm normal prepurge.

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Source: Carrier 59TP6A Installation, Start-up, Operating and Service Instructions, Fig. 66 Troubleshooting Guide (cont.), p.89; Sequence of Operation, p.85. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.