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Carrier Rapid flashing: Line voltage (115 VAC) polarity reversed. If twinned, check 24 V transformer phasing

Ref. CARRIER-RAPID-FLASHING · From the Carrier furnace manual · Updated 2026-10-23

Status codeRapid flashingCarrier
What it means

Line voltage (115 VAC) polarity reversed. If twinned, check 24 V transformer phasing.

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How it shows: Status LED flashing rapidly without a pause

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§1Likely causes

  • Reversed line-voltage polarity
  • Improper low-voltage transformer phasing on twinned units

§2Safe DIY steps

  1. Techniciancheck for correct line voltage polarity
  2. Technicianif twinned, refer to twinning kit instructions
Safety firstIf you smell gas, do not touch any electrical switch or use a phone in the building; leave immediately and call your gas supplier from outside. Turn off electrical power at the furnace switch or breaker before opening any panel, and never bypass or jumper a limit, rollout or pressure switch. Gas valve, burner, venting, wiring and control-board work should be done by a licensed HVAC technician.

§3When to call a pro

Call a licensed HVAC technician: line-voltage wiring must be corrected by a qualified person.

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§4Other Carrier codes

13Carrier

Limit circuit lockout: a limit or flame rollout switch was open longer than 3 minutes. Control auto-resets after 3 hours (see code 33).

14Carrier

Ignition lockout: system failed to ignite gas and prove flame in 4 attempts. Control auto-resets after 3 hours (see code 34).

21Carrier

Gas heating lockout. Control will NOT auto-reset.

22Carrier

Abnormal flame-proving signal: flame is proved while the gas valve is de-energized. Inducer runs until the fault is cleared.

23Carrier

Pressure switch did not open.

31Carrier

Low (LPS) or high (HPS) pressure switch did not close or reopened.