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Carrier · Furnace

Rapid Flash Reversed 115-V polarity (or twinning phasing)

High severity 59TP6A58SB0A/58SB1A

What the control is telling you

LED blinks rapidly with no pause and the furnace will not heat; line-voltage polarity is reversed, or on twinned units the 24-V transformers are out of phase.

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

Likely causes

  • 115-V line and neutral reversed
  • Twinned furnaces with incorrect 24-V transformer phasing
  • Missing earth ground (control needs it)

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 incoming 115-V wiring against the field wiring diagram (Fig. 34) and correct polarity.
  3. Make sure the furnace has a proper earth ground; gas piping must not be used as the ground.
  4. If units are twinned, check the low-voltage (24 V) transformer phasing between furnaces.
  5. Restore power and confirm the LED goes to continuous ON.

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Source: Carrier 59TP6A Installation, Start-up, Operating and Service Instructions, Fig. 66 Troubleshooting Guide, p.88; Electrical Controls and Wiring, p.76. 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.