Carrier & Bryant Furnace and Heat Pump LED Flash Codes
How to read the status LED on a Carrier or Bryant furnace or heat pump, what codes 13, 14, 31, 33 and others mean, and which ones you can safely handle yourself.
Carrier & Bryant Furnace and Heat Pump LED Flash Codes
Carrier and Bryant furnaces and heat pumps report faults by flashing a status LED on the control board. Most furnaces use a two-digit code: count the short flashes for the first digit, then the long flashes for the second. Three short flashes followed by three long ones is code 33. The tables below come from Carrier's own installation and wiring documents. Each one names the equipment it covers, because the code list on your unit's door label is the one that counts.
Bryant is a Carrier brand, and many Bryant furnaces and heat pumps use the same family of controls. Even so, check the service label on the inside of the blower or control-box door before you rely on any table. That label is printed for your exact model.
Reading the furnace status LED
Carrier's 58SB0A/58SB1A furnace manual describes three LED states. The light can be on continuously, rapid flashing, or flashing a two-digit code. You can see it through the sight glass in the blower access door, so you don't need to remove anything.
- Rapid flashing means the 115-volt polarity is wrong, and the furnace will not operate. That's a wiring problem for an electrician or HVAC technician.
- Write the code down before you cut power. On controls with a red LED, stored codes are erased when 115V or 24V power is interrupted. Turning the furnace off at the switch can wipe out the most useful clue.
Furnace status codes (Carrier 58SB0A / 58SB1A, single-stage 80% gas furnace)
| Code | What it means | What you can safely check | When to call |
|---|---|---|---|
| 11 | No previous code. Stored codes clear after 72 hours | Nothing; no stored fault | — |
| 12 | Blower on after power-up. Normal: the blower runs 90 seconds if power is restored during a call for heat | Nothing | — |
| 13 | Limit circuit lockout: a limit, draft safeguard, flame rollout or blocked-vent switch was open longer than 3 minutes. Auto-resets after 3 hours | Replace a dirty filter; open closed supply registers | Always find out why a limit opened. Rollout switches need a technician |
| 14 | Ignition lockout: failed to light and prove flame in 4 attempts. Auto-resets after 3 hours | Make sure the furnace's gas shut-off valve is on | If it locks out again |
| 21 | Gas heating lockout | Nothing user-serviceable | Control relay or gas valve wiring |
| 22 | Abnormal flame-proving signal: flame sensed while the gas valve is off. The inducer keeps running | Nothing user-serviceable | Right away. Stuck-open or leaky gas valve |
| 23 | Pressure switch did not open | Nothing user-serviceable | Pressure tube or switch |
| 24 | Secondary (24V) fuse open: short in the low-voltage wiring, including thermostat wires | Nothing user-serviceable | Find the short before the fuse is replaced |
| 31 | Pressure switch didn't close, or reopened | From outside, check that the vent and intake pipes aren't blocked by snow or debris | Inducer, pressure switch, venting or combustion air |
| 33 | Limit circuit fault: limit, draft safeguard, flame rollout or blocked-vent switch open | Replace a dirty filter; open supply registers | If it repeats or turns into 13 |
| 34 | Ignition proving failure: flame not sensed during trial for ignition | Confirm the furnace's gas shut-off valve is on | Flame sensor, igniter or gas valve diagnosis |
| 45 | Control circuitry lockout. Auto-resets after 1 hour | Reset power once, per the manual | If it repeats, the control board needs replacing |
Carrier's troubleshooting guide lists a dirty filter or restricted duct system first among the causes of code 33. Changing the filter really is the first thing to try. The flame rollout switch and blocked-vent shutoff switch need a manual reset, and a tripped rollout switch is a warning about combustion or venting. Don't keep resetting it. Have it diagnosed.
Heat pump status codes (Carrier 25HPA6 Performance two-stage heat pump)
The outdoor control board on the 25HPA6 uses the same short-then-long flash scheme. These codes come from the wiring diagram Carrier prints for the unit.
| Code | What it means | What you can safely check | When to call |
|---|---|---|---|
| On, no flash | Standby | — | — |
| 1, pause | Running low stage | — | — |
| 2, pause | Running high stage | — | — |
| 16 | System communications failure | Check the thermostat has power | If it persists |
| 25 | Invalid model plug | Nothing user-serviceable | Control configuration |
| 31 | High-pressure switch or discharge temperature switch trip | Clear leaves, snow and debris from the outdoor coil; replace the indoor filter | If it repeats |
| 32 | Low-pressure switch trip | Replace the indoor filter | Refrigerant or airflow diagnosis |
| 45 | Control fault | Nothing user-serviceable | Board diagnosis |
| 46 | Brownout (230V) | Note any building power issues | If it repeats |
| 47 | No 230V with a call to run | Check the outdoor disconnect and the breaker | If power is on and the code remains |
| 53 | Outdoor air temperature sensor fault | Nothing user-serviceable | Sensor replacement |
| 55 | Coil temperature sensor fault | Nothing user-serviceable | Sensor replacement |
| 71 / 72 | Low / high stage thermal cutout | Nothing user-serviceable | Compressor diagnosis |
| 73 | Contactor shorted | Nothing user-serviceable | Contactor replacement |
| 74 | Contactor open (no 230V to compressor) | Nothing user-serviceable | Contactor or wiring |
| 81 / 82 | Low / high stage thermal lockout (4 hours) | Nothing user-serviceable | Compressor diagnosis |
| 83 | Low-pressure lockout (4 hours) | Nothing user-serviceable | Refrigerant diagnosis by an EPA-certified technician |
| 84 | High-pressure lockout (4 hours) | Clear the outdoor coil | Fan, coil or refrigerant diagnosis |
The same board has a five-minute short-cycle protector. After the outdoor unit shuts off, there's a built-in delay before the compressor restarts. A heat pump that sits idle for a few minutes after you change the thermostat isn't broken.
What's safe to try
- Read and record the code first. Look through the sight glass, count the flashes twice to be sure, and write the code down before you touch any switch.
- Replace the furnace filter. It's the most common cause of limit codes 13 and 33, and of the pressure trips on a heat pump.
- Check the gas shut-off valve and the breakers. Make sure the furnace's gas valve handle is on and the furnace switch and breaker are on. For the heat pump, make sure the outdoor disconnect and breaker are on.
- Look at the vents and the outdoor unit. Clear snow from high-efficiency vent and intake pipes, and clear debris from around the heat pump. Look, don't take anything apart.
- Allow the automatic reset. Furnace codes 13 and 14 reset on their own after 3 hours, and 45 after 1 hour. Repeatedly cycling power to get around a lockout hides the real problem.
If you smell gas, don't touch any switch. Leave the building and call your gas utility or 911 from outside. Never bypass a limit, rollout or pressure switch, never open the gas valve or burner compartment, and leave refrigerant work to EPA-certified technicians.
When to call a technician
- Code 22 (flame sensed with the gas valve off). Call right away.
- Any lockout that comes back after the automatic reset (13, 14, 45, heat pump 81–84).
- Code 24. A blown low-voltage fuse means there's a short somewhere, and a new fuse will just blow again.
- Repeated 31, 33 or 34 on a furnace with a clean filter.
- Any heat pump code that points to a sensor, the contactor, the compressor or refrigerant pressure.
When you call, have the model number from the rating plate and the exact flash code ready.
Our independent, EPA-certified technicians work on Carrier and Bryant equipment across Manhattan and the other four boroughs. We offer 24/7 emergency service for no-heat calls and give you upfront pricing before work starts. See Carrier central AC and heat pump repair and heating system installation, or request service with your code.
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