What do the blinking light codes on a Carrier furnace mean?
A Carrier furnace flashes a two-digit LED code, and our Twin Cities $79 trip charge is waived with an approved repair. Short flashes give the first digit, long flashes the second. Code 14 is an ignition lockout; 32 is a low pressure switch that didn't close.
Key points
- Carrier's troubleshooting guides read each code as short flashes (first digit) then long flashes (second digit), so 3 short and 4 long is code 34.
- Look through the sight glass and write the code down before touching power. On one Carrier guide, removing the blower door erases the stored codes.
- Pressure switch codes (31, 32, 43) point to venting, the condensate drain or the inducer. Limit and rollout codes (13, 33) mean stop and call.
- Codes differ by model and control board, so the chart on your furnace door or in its manual wins over any list online, including this one.
- Never jump or bypass a safety switch, and never reset a lockout over and over.
A Carrier furnace flashes a two-digit LED code: short flashes give the first digit and long flashes give the second, so three short and four long is code 34, an ignition-proving failure. Code 14 is an ignition lockout and code 32 is a low pressure switch that didn't close. Count the short flashes, wait through the pause, then count the long ones. This guide decodes the common codes from Carrier's own troubleshooting guides, then shows what you can safely check yourself. Our general post on what the blinking light on a furnace means covers other brands too.
Which Carrier documents is this based on?
The codes come from two Carrier troubleshooting guides published on Carrier's residential site. The first is the 59MN7A Series 100 Troubleshooting Guide (form 59MN7A-01T) for Carrier's variable-speed, modulating condensing furnace, which uses an amber LED. The second is Carrier form 58-3T, the Troubleshooting Guide for its Deluxe 2-stage, 80% non-condensing furnaces (58UHV, 58TUA, 58TMA and related models), which uses a red LED.
The two guides agree on the basic code format and on most numbers. They also differ in places, and that is the point of the next section.
Why your chart matters more than this list
Fault codes are tied to the control board, not to the badge on the door. The 59MN7A guide has codes the 2-stage guide does not (15 blower motor lockout, 35 gas valve fault, 41 blower motor fault, 42 inducer motor fault). Other Carrier-family brands, including Bryant, Payne and Day & Night, are Carrier brands according to Carrier's brands page, but no document confirms their charts are identical, so don't assume it.
To find your own chart:
- Look for a label on the inside of the furnace door or on the control board cover. Many furnaces print the code list there.
- Find the model number on the rating plate inside the cabinet and search that exact number plus "installation instructions" on the manufacturer's website.
- Photograph both before you call us. With the model number and the exact flash count, a technician can often tell you what is likely wrong before arriving.
How do you read the light safely?
- Leave the blower door on. Carrier's 59MN7A guide tells technicians not to remove the blower door and to record the LED status first. Its 2-stage guide says removing the blower door interrupts power and erases the previous status codes.
- Look through the sight glass. If your door has a small window, the LED is visible there. Use a flashlight if needed.
- Watch the whole pattern. Count the short flashes, wait for the pause, then count the long flashes. Watch it repeat at least twice.
- Write it down before you touch the thermostat, the furnace switch or the breaker. Cycling power can wipe the code you came to read.
A steady light means the control has 24-volt power. No light means no power at the board: check the furnace switch, the breaker and that the blower door is seated.
Carrier status codes at a glance
These meanings come from the two Carrier guides above. Always compare to the chart on your own furnace.
| Code | What Carrier says it means |
|---|---|
| Rapid flashing | Line voltage polarity reversed |
| 11 | No previous code stored |
| 12 | Blower on after power-up (normal if powered up during a call for heat) |
| 13 | Limit or flame rollout switch lockout; auto resets after 3 hours |
| 14 | Ignition lockout; auto resets after 3 hours |
| 21 | Gas heating lockout; does not auto reset |
| 22 | Abnormal flame-proving signal (flame sensed with the gas valve off) |
| 23 | Pressure switch did not open |
| 24 | Secondary (24-volt) fuse is open |
| 31 | Medium or high pressure switch (or relay) did not close or reopened |
| 32 | Low pressure switch did not close or reopened |
| 33 | Limit or flame rollout switch is open |
| 34 | Ignition-proving failure |
| 43 | Low or medium pressure switch open while the higher switch is closed |
| 45 | Control circuitry lockout (replace the control if it repeats) |
Codes 15, 35, 41 and 42 appear only in the 59MN7A guide: blower motor lockout, gas valve fault, blower motor fault and inducer motor fault.
What do the common code families mean?
Pressure switch (23, 31, 32, 43). The furnace could not prove the inducer is moving exhaust. For code 32, Carrier lists a restricted vent, a plugged condensate drain, water or a sagging section in the vent pipe, excessive wind, and disconnected or blocked pressure tubing. In a Minnesota winter, frost or snow over the PVC vent and a frozen condensate drain top the list. See our guide to the furnace pressure switch.
Flame sense and ignition (14, 34). Code 34 means the furnace tried to light and could not prove flame; the control tries three more times before locking out as 14. Carrier lists oxide buildup on the flame sensor, a defective igniter, a gas valve that is turned off or defective, a poor ground and low inlet gas pressure.
Limit and rollout (13, 33). The limit or rollout circuit is open. Carrier lists a dirty filter or restricted ductwork, a loose blower wheel and a defective switch among the causes. The flame rollout switch needs a manual reset, which is a technician's job, because rollout means flame came out of the burner area. Read what a furnace limit switch does.
Lockouts (13, 14, 21, 45). A lockout is the furnace protecting itself after repeated failures. Resetting it does not fix what caused it.
Safe checks before you call
- Thermostat: set to Heat, a few degrees above room temperature, with fresh batteries if it takes them.
- Furnace switch and breaker: the switch near the furnace is on, the breaker has not tripped, and the blower door is seated against its switch.
- Filter: replace a clogged one. A dirty filter is the most common cause of limit trips.
- Vents outside: on a high-efficiency furnace, clear snow and frost from the PVC intake and exhaust by hand.
- Condensate: look for water around the furnace or a trap that looks frozen or backed up. Do not pour anything hot into the line.
- Gas valve: note whether the lever on the valve is in line with the pipe (open) or across it. If you find it closed, do not force it. Tell us what you found.
- One reset at most: after clearing a vent or changing a filter, turn the furnace switch off for a minute and back on, and watch one cycle.
When to stop and call
Call if the same code returns after one reset, if you see 13, 33, 21, 22 or 45, if the light is rapid-flashing or off with power on, or if the furnace shows a different code each cycle. Nationally, HomeGuide puts typical repair parts behind these codes at $150–$400 for a pressure switch, $80–$250 for a flame sensor replacement and $300–$650 for a control board. With us, you get a written, flat-rate price before work starts.
We service Carrier and its sister brands (we're an independent contractor, not a Carrier dealer): see our Carrier service page or book furnace repair in Minneapolis. We are open 7 days, 7am to 9pm, and no-heat calls get priority. Call 612-429-3465 with the code and your model number.
Common questions about heating
What does code 14 mean on a Carrier furnace?
In both Carrier troubleshooting guides, 14 is an ignition lockout. The furnace tried to light and could not prove flame, so it shut down. Both guides say the control resets itself after three hours and send technicians to code 34 for the causes, such as a dirty flame sensor, a weak igniter or a gas valve problem.
What does a rapid flashing light on a Carrier furnace mean?
Both Carrier guides say rapid flashing means the 115-volt line power has its polarity reversed. That is a wiring problem, often after electrical work or a new install, and the furnace may refuse to run gas heat. It is a job for a technician or electrician, not a reset.
Will unplugging the furnace clear a Carrier error code?
It can. Carrier's guide for its 2-stage 58-series furnaces says stored status codes are erased when power to the control is interrupted. That is why you read the code first and write it down. A cleared code does not fix the cause, and a real fault will come back on the next call for heat.
What do Carrier furnace codes 13 and 33 mean?
Limit and rollout codes such as 13 and 33 mean stop and call a technician. Don't reset the furnace repeatedly, and never jump or bypass a safety switch. Codes differ by model and control board, so the chart on your furnace door or in its manual wins over any list online.
Sources
- Carrier's residential site carrier.com
- HomeGuide: furnace repair costs homeguide.com