Carrier Error Codes & Diagnostics
Complete diagnostic directory for official Carrier fault codes. Verify root causes, safe troubleshooting steps, and replacement part numbers before calling a technician.
Carrier status code 13: the lockout that follows a limit or rollout switch
Carrier lists status code 13 as a limit or flame rollout switch lockout. The control had already seen that circuit open, reported it, and then decided the condition had lasted long enough to stop trying. A lockout is a deliberate refusal to restart, so code 13 is a stronger statement than the open-circuit code that precedes it. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, as covered by troubleshooting guide 58-3T This reading is taken from Carrier troubleshooting guide 58-3T, which covers deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors. Other Carrier furnace controls, and the same numbers on Bryant or Payne equipment, are read from their own literature. Confirm the model on the furnace rating plate first. Owner-safe checks: With the furnace switched off, inspect the return-air filter and fit a clean one of the specified size and type if it is loaded. | Walk the house and confirm that supply registers and return grilles are open and not covered by furniture, rugs, or stored items. | Record the flash pattern through the sight glass without opening the blower door, along with the date and time of the lockout. Qualified technician: Identifying which safety device opened, measuring temperature rise, and inspecting combustion and venting are licensed gas-furnace tasks. | Treat soot, scorching, an odour of combustion products, or a carbon monoxide alarm as an immediate stop. Get fresh air into the space, keep the appliance off, and use the emergency number your gas supplier publishes.
Carrier status code 14: ignition lockout after four failed trials
Status code 14 on this Carrier control is ignition lockout. The guide states that lockout occurs after four consecutive unsuccessful trials for ignition and that the control resets itself automatically after three hours. The number 14 therefore counts failures; it does not identify which part of the ignition sequence failed. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, covered by troubleshooting guide 58-3T The count of four trials and the three-hour automatic reset are stated in Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. Single-stage and modulating Carrier controls, and the same number on other manufacturers, follow their own literature and their own retry counts. Owner-safe checks: Confirm that other gas appliances in the property are working normally, which separates a supply-wide interruption from a furnace-specific fault. | Check that the thermostat is calling for heat and that its batteries, if fitted, are good, so a failed call is not mistaken for a failed ignition. | Note the time of each lockout and the weather conditions, then leave the furnace off rather than forcing repeated retries. Qualified technician: Measuring gas pressure, testing igniter resistance, cleaning or replacing a flame sensor, and inspecting venting are licensed gas-furnace tasks. | A smell of gas at any point is an emergency. Leave the property, avoid switches and flames, and contact the emergency number for your gas supplier before anything else.
Carrier Infinity code 16 with 53, 55 or 47: telling a communication fault from a failed sensor
Read the number as a pair before deciding anything. On 24VNA6 and 25VNA4 equipment the outdoor board reports a base code plus an expansion code, so 16, 53 and 55 occupy different columns of one table and carry different meanings depending on the column they came from. A genuine loss of communication with the Infinity System Control sets no diagnostic fault at the outdoor unit: the service manual says the Comm light goes off and the equipment falls back to its discrete control inputs. Applies to: Carrier Infinity System Control paired with communicating equipment, with the outdoor-unit code structure documented for 24VNA6 and 25VNA4 variable-speed units The code structure described here is the one published for the 24VNA6 and 25VNA4 outdoor units. Carrier furnaces, fan coils and older Infinity outdoor sections keep their own tables, and a two-digit number copied from one of those is not evidence about a variable-speed unit carrying this board. Owner-safe checks: Photograph the wall control message, the outdoor display, and the state of the Comm light before any power is interrupted. | Write down whether the number appeared in a code position or in a temperature field on a status screen. | Note which modes the system still accepts, because a mode that runs is evidence about what the control is protecting. Qualified technician: Resistance measurement at the control board connector, and any inspection inside the outdoor cabinet, is qualified service work. | Tracing the communication path between the outdoor board and the Infinity System Control involves energised low-voltage wiring and belongs to a technician.
Carrier status code 24: the secondary voltage fuse is open
Carrier defines status code 24 as the secondary voltage fuse being open. That fuse protects the 24-volt control circuit, and the guide specifies a 3 amp automotive blade type that must be replaced only with another 3 amp fuse. A fuse opens because something drew more current than the circuit allows, so the fuse is the symptom. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T The fuse rating and the code definition come from Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. Fuse ratings differ between control platforms, and fitting anything other than the rating in the literature for your exact model removes the protection the circuit was designed around. Owner-safe checks: Establish exactly what has stopped: heating alone, heating and cooling together, or any accessory such as a humidifier. | Check whether the thermostat display is blank or still powered, since that alone tells the technician which side of the circuit lost supply. | Write down any recent work on thermostats, cabling, outdoor equipment, or the building fabric in the weeks beforehand. Qualified technician: Locating a short in the 24-volt circuit, testing the transformer, and replacing the control fuse are tasks inside an enclosure that also carries line voltage, so they belong to a qualified technician. | Never fit a fuse of a higher rating than the literature specifies. The protection the original rating provides is the reason the transformer and board survived the fault.
Carrier furnace status code 31: pressure switch did not close
Carrier assigns status code 31 to a high-heat pressure switch input that did not close when the control called for high or intermediate heat, or that opened during the heat cycle. It reports the state of a proving circuit, so the draft inducer, venting, condensate, tubing, wiring, and the switch itself all stay on the list until one is confirmed. Applies to: Carrier two-stage and variable-speed modulating condensing furnaces that report status code 31 This reading follows Carrier service literature for two-stage and modulating condensing furnaces that flash a two-digit status code. Single-stage models and other code numbers behave differently, and the legend printed inside the furnace door is what confirms the meaning for a given board. Owner-safe checks: With the furnace off, clear any frost, ice, snow, or debris from the outdoor vent and intake terminations and confirm the terminations are not obstructed. | Check the furnace filter is clean, the return and supply grilles are open, and the furnace access door is fully closed. Qualified technician: Measuring inducer pressure, testing the switch and inducer, clearing the condensate trap, and any wiring or gas-valve work require a qualified heating technician, and the pressure switch must never be bypassed.
Carrier status code 32: three switches share one number
Carrier writes status code 32 as the low-heat pressure switch, the draft safeguard switch, or the downflow auxiliary limit switch failing to close or reopening after it had closed. Three separate devices share the entry, and the control cannot tell you which one acted, so the code narrows the fault to a group rather than to a part. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T Guide 58-3T is the source here, and it covers deluxe two-stage induced-combustion equipment only. The auxiliary limit named in the entry is present on downflow arrangements, so what the code can mean depends on how your furnace is installed as well as on which model it is. Owner-safe checks: Look at the outdoor vent and intake terminations from ground level and note any ice, snow, nesting material, or vegetation without attempting to clear anything at height. | Time how long the furnace produces heat before it stops, and whether the burners lit at all. | Keep a short log of the outdoor temperature and wind conditions each time the code appears. Qualified technician: Measuring draft pressure, inspecting the vent system, clearing condensate traps, and testing pressure switches are licensed gas-furnace tasks. | Combustion products detected indoors, or a carbon monoxide alarm sounding, outranks every other instruction on this page. Get people out, open up the space, and call the emergency line your gas supplier publishes.
Carrier 58MCB code 33: limit circuit fault is two different warnings
Carrier 58MCB status code 33 means the limit circuit is open. That circuit includes the high-limit switch and flame-rollout switches, so the code does not tell you which safety opened. Check only the filter and unobstructed grilles; visible flame rollout, soot, a gas odor, or a returning code requires immediate service. Applies to: Carrier 58MCB Series 110 and 120 condensing gas furnaces This interpretation is limited to the Carrier 58MCB Series 110 and 120 manual. Other Carrier furnace controls can use the same number with different timing or component groupings, so confirm the model on the furnace rating plate. Owner-safe checks: With the furnace off, inspect only the normal homeowner-access filter and replace it with the specified size and type if loaded. | Confirm return grilles and supply registers are open and clear without reaching into ducts or removing furnace panels. | Record the full flash pattern, operating sequence, and any later code before power is interrupted. Qualified technician: Identifying the open device, measuring temperature rise, testing safeties, and inspecting combustion require licensed gas-furnace service. | A rollout indication, soot, gas odor, or carbon-monoxide alarm is a stop condition, not a reset opportunity.
Carrier status code 34: ignition proving failed on this trial
Carrier lists status code 34 as an ignition-proving fault. It records that a trial for ignition did not end with a proven flame, and unlike code 14 it does not mean the control has given up. Seeing 34 without 14 means the furnace is still retrying, which is the moment when observing what happens is worth most. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T Read here from Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. The relationship between the per-trial fault and the lockout that follows it is specific to this control family, and other manufacturers using the number 34 are not describing the same thing. Owner-safe checks: Listen to a full heating cycle from a safe distance and note whether a flame is established at all, and whether it is lost after establishing. | Keep a tally over several days of how many heat calls succeed and how many fail, with the times of day. | Confirm that other gas appliances behave normally and note whether failures coincide with their use. Qualified technician: Measuring the flame signal, testing igniter resistance, cleaning a sensing electrode, and checking manifold gas pressure are licensed gas-furnace tasks. | Any smell of gas requires the emergency response for your supplier before any further troubleshooting: leave the property, avoid switches, and call from outside.