OEM HK42FZ / CEPL130438 / 50M56X-843 Control Family • 2-Digit Short + Long Amber LED
Carrier, Bryant & Payne Furnace Code 31, Code 33 & 2-Digit Blink Decoder
⚡ Instant OEM Answer (Carrier / Bryant / Payne 2-Digit LED System):
Carrier, Bryant, and Payne furnaces flash SHORT amber blinks for the first digit (tens) and LONG amber blinks for the second digit (ones). Code 31 (3 short, 1 long) means an open Pressure Switch (
-0.65" WC, 56% caused by a clogged white condensate trap); Code 33 (3 short, 3 long) means an open High Limit Switch; and Code 14 (1 short, 4 long) is 3-hour ignition lockout (LH33WZ511 sensor below 0.7 µA DC or LH33ZS004 igniter outside 40–90 Ω).
Complete OEM Reference Chart
Carrier, Bryant & Payne 2-Digit Error Code Master Matrix
Applies to Carrier WeatherMaker & Comfort/Performance series (58MVB, 58MCA, 58STA, 58PAV, 59SC5, 59TP6), Bryant Plus 80/90 & Evolution (310AAV, 350MAV, 912SB, 926TB), and Payne (PG8MAA, PG9MAB, PG95SAS) furnaces using HK42FZ004, HK42FZ009, HK42FZ013, HK42FZ018, HK42FZ034, or White-Rodgers 50M56X-843 control boards.
| 2-Digit Code | Amber LED Cadence | OEM Fault Description | Primary Fix & OEM Part SKU |
|---|---|---|---|
| Steady ON | Solid Continuous Amber | Normal Standby / Active Heat | Healthy 24VAC control power & intact 3A purple fuse. Check thermostat W call. |
| Code 12 | 1 Short + 2 Long | Blower On After Power-Up (90s Purge) | Normal 90-second blower purge whenever 120V power restores during a heat call. |
| Code 13 | 1 Short + 3 Long | Limit Circuit 3-Hr Lockout (>3 Min Open) | Escalated from Code 33; inspect manual Flame Rollout switch, blower capacitor, and HH18HA Primary Limit. |
| Code 14 | 1 Short + 4 Long | Ignition Lockout (4 Failed Trials) | Cycle 120V for 30s; polish LH33WZ511 Flame Sensor (2.0–5.0 µA DC) or swap LH33ZS004 Igniter (40–90 Ω). |
| Code 21 | 2 Short + 1 Long | Gas Heating Lockout (Abnormal Gas Valve Sense) | 24VAC detected on gas valve circuit when valve should be off. Inspect EF32CW valve harness & board relay. |
| Code 22 / 23 | 2 Short + 2/3 Long | Abnormal Flame-Proving Signal / Stuck PS Closed | Code 22 = false flame sensed with gas off; Code 23 = pressure switch welded closed before inducer start. |
| Code 24 | 2 Short + 4 Long | Secondary 24VAC Fuse Open | Replace blown 3-Amp purple ATC automotive blade fuse; inspect outdoor AC contactor 2-wire cable for shorts. |
| Code 31 | 3 Short + 1 Long | Pressure Switch Did Not Close or Reopened | Flush white plastic condensate trap & re-prime, clear PVC vent ice, test HK06NB124 switch (-0.65" WC). |
| Code 32 | 3 Short + 2 Long | Low-Stage Pressure Switch Did Not Close | Two-stage 58MVB/59TP6 furnaces: flush condensate trap and inspect low-heat collector port. |
| Code 33 | 3 Short + 3 Long | Limit or Flame Rollout Switch Open | Replace clogged MERV filter immediately, open supply vents, check PSC blower run capacitor µF. |
| Code 34 | 3 Short + 4 Long | Ignition Prove Failure (Active Retry) | Active precursor to Code 14; polish flame sensor rod and clean rusty burner crossover slots. |
| Code 45 | 4 Short + 5 Long | Control Circuitry Lockout (1-Hour Auto-Reset) | Internal microprocessor check fault; if persistent after 120V reset, swap with White-Rodgers 50M56X-843. |
⚠️ Carrier 58MCA / 58MVB & Bryant 350MAV Code 31/13 Field Advisory:
If a 1993–2011 90%+ condensing Carrier/Bryant furnace repeatedly throws Code 31 or Code 13 even after the condensate trap and PVC pipes are clean—accompanied by a sharp aldehydic/chemical smell outdoors at the PVC exhaust—have a licensed HVAC technician perform a flue Carbon Monoxide (CO) test to check for polypropylene-lined secondary heat exchanger delamination (covered under Carrier Extended Bulletin/Warranty programs on qualifying units).