A status code is the most useful thing a Carrier furnace tells you and the most commonly misread. The number narrows the fault to a subsystem, but it does not name the failed part, and the place you read it differs completely between a conventional furnace and a communicating one. Get that distinction wrong and you will spend an hour looking for a blinking light that does not exist, or counting blinks on a furnace that is actually fine. This page is the Carrier-specific companion to our general furnace repair service and our Carrier furnace repair page.
Two systems, two places to read the code
This is the distinction that trips up almost everyone, so it is worth being explicit before we touch a single code number.
- Conventional Carrier furnaces (Performance 59TP6, Comfort 58STA, Bryant 313AAV, and essentially everything before the communicating platform) report faults with an amber status LED behind the lower burner door. The light blinks the code as two digits — it flashes the first digit, pauses, then flashes the second. You physically count the blinks. Three blinks, pause, one blink is code 31.
- Communicating Infinity and Evolution systems (the 59MN7 variable-speed furnace paired with an Infinity Touch wall control) do not use a blinking LED you count. The system stores faults as numeric codes and you read them in the Last 10 System Events screen under the wall control’s Service menu. The same fault that blinks as a code on a conventional furnace appears here as a number on a screen.
The meanings of the numbers are consistent across both, which is why this confusion is so common: a homeowner reads “code 31” online, goes looking for a blinking light, and never finds it because their Infinity system reports it on the wall control instead. Below, each code notes both contexts.
Carrier furnace status code 13 — Limit Lockout
What it means: Carrier’s published fault list labels code 13 a furnace Limit Lockout (limit circuit lockout). The high-limit or flame-rollout safety switch has been open long enough that the control board has stopped trying to run and locked the furnace out. On conventional units this lockout typically lasts a set period (often around three hours) or until power is cycled.
How it shows: on a conventional furnace, the amber LED blinks one, pause, three. On an Infinity system, it appears as code 13 in Last 10 System Events.
Why it happens: almost always restricted airflow that overheats the furnace — a heavily clogged filter is the number-one cause, followed by blocked return or supply registers, closed-off ductwork, or a weak blower. Code 13 is usually code 33 that was never resolved (see below). The fix starts with airflow: filter, registers, blower amp draw, and a check of the heat exchanger and limit switch.
Carrier furnace status code 31 — Pressure Switch / High Pressure Switch Open
What it means: Carrier’s fault list labels code 31 a furnace High Pressure Switch Open — the high-heat pressure switch (or relay) did not close when the inducer started, or it opened during the cycle. The pressure switch proves the draft inducer is actually venting combustion gases outside before the control allows the gas valve to open. No proven draft, no ignition.
How it shows: conventional furnaces blink three, pause, one. Infinity systems list code 31 in Last 10 System Events.
Why it happens: a clogged condensate trap on a condensing furnace (the most common cause we find), a blocked or sagging vent, a weak draft inducer, or occasionally the switch itself. We meter the switch and the inducer before replacing anything — the switch is usually the messenger, not the fault. Full detail and pricing on our Carrier furnace pressure switch & code 31 page.
Carrier furnace status code 33 — Limit Fault
What it means: Carrier’s fault list labels code 33 a furnace Limit Fault (limit circuit fault). The high-limit or flame-rollout switch has opened — the furnace got too hot. On conventional units the blower runs to cool the furnace, and the documented behavior is that if the switch stays open longer than about three minutes the code escalates to a code 13 lockout; if it re-closes sooner, the furnace retries.
How it shows: conventional furnaces blink three, pause, three. Infinity systems list code 33 in Last 10 System Events.
Why it happens: restricted airflow is the overwhelming cause — most code 33 faults trace to a heavily clogged air filter starving the blower of the air it needs to move heat away from the exchanger. Other causes: closed registers, a dirty blower wheel, a failing blower motor, or a genuinely failing limit switch. A common real-world trigger is a homeowner installing a too-restrictive high-MERV filter; the airflow drops, the furnace overheats, and the limit trips. Change the filter first; if 33 persists, it needs a metered look.
How the Infinity Touch fault history works
On a communicating system, faults are not just flashed and forgotten — they are stored. When a fault occurs, the Infinity Touch main screen shows a System Malfunction message, and the detail lives in the Last 10 System Events screen under the Service menu. The communicating equipment keeps its own fault history: the indoor furnace or fan coil and the outdoor unit each store their recent faults, so a technician can see whether the problem is on the heating side, the cooling side, or the communication bus between them. Carrier stores these event descriptions in permanent memory so the history survives a power cycle — which is exactly why “just reset it” is bad advice: you lose nothing by leaving it for the technician to read, and you may lose the trail if you start cutting power and clearing things. The same four-wire ABCD communication bus that carries this data is itself a common fault point; we cover that on our Carrier AC repair page.
Other Carrier furnace status codes
Codes 13, 31, and 33 are the ones we field most, but Carrier publishes a full list. The following are taken directly from Carrier’s own Residential Communicating System Master Fault Code List (technical bulletin TIC 2019-0002); on conventional furnaces the same numbers blink on the amber LED. This is a reference for what the number points at — not a repair prescription, since each still needs a metered diagnosis:
| Code | Carrier description (furnace) |
|---|---|
| 12 | Blower on after power-up |
| 13 | Limit lockout |
| 14 | Ignition lockout |
| 15 | Blower lockout |
| 21 | Gas heat lockout |
| 22 | Flame sense error |
| 23 | LPS or HPS closed |
| 24 | 24VAC fuse open |
| 31 | High pressure switch open |
| 32 | Low pressure switch open |
| 33 | Limit fault |
| 34 | Ignition fault |
| 41 | Blower motor fault |
| 42 | Inducer fault |
| 43 | LPS open, HPS closed |
Codes 14 (ignition lockout) and 34 (ignition fault) usually point at the no-heat ignition chain we walk through on our Carrier furnace not heating page; code 22 (flame sense) is the “lights then drops out” flame-sensor signature covered there too.
Reading the code is the start, not the fix
Here is the honest part. A code is a subsystem, not a part. Code 31 can be a $0 clogged-trap clean or a $580–$1,100 inducer. Code 33 can be a filter you change yourself or a limit-and-heat-exchanger problem you should not ignore. We read the code on arrival, then confirm it on the meter — flame-sense microamps, draft pressure at the inducer, limit-switch continuity, blower amp draw — and only then name the part. We do not guess from the code alone, and we do not jumper a safety switch to force a furnace to run. The flat $89 diagnostic ($149 after-hours) credits to the repair, so the read-and-confirm step costs you nothing if you proceed.
The SoCal first-cold-night pattern
Most of these codes surface on the same night. An LA-basin furnace runs 200–400 hours a year against 1,500-plus in a cold climate, sitting idle from April through October. Over that long off-season the flame sensor collects dust (code 22), the condensate trap clogs (code 31), the filter quietly loads up and the limit trips on the first hard fire (codes 33 and 13), and the ignitor cracks (the ignition chain behind codes 14 and 34). The first November cold snap stress-tests all of it at once, which is why the first cold week is our busiest furnace stretch of the year. Mountain installs in Big Bear and Wrightwood run real heating hours and fail on a wear curve instead. Fall maintenance in October is the cheapest insurance — the related airflow and cycling chain is in our furnace short-cycling guide.
Carrier furnace diagnostic pricing
Reading and confirming the code is the $89 diagnostic ($149 after-hours), credited to the repair. The repair price follows the cause, flat-rate from our SoCal tickets: flame sensor $185–$295, hot-surface ignitor $245–$485, gas valve $385–$685, IFC control board $480–$950, blower motor $480–$890, draft inducer $580–$1,100. A cracked heat exchanger ($1,500–$3,500) is the one fault where we quote replacement against repair and red-tag the furnace if it is leaking. Full table on our Carrier furnace repair page.
Carrier and Bryant
Bryant and Carrier are the same corporation and share the control platform. A Bryant Legacy 313AAV is the Carrier 58STA under different badging, with the same IFC board and the same status-code logic; conventional Bryant furnaces blink the same patterns, and Bryant Evolution communicating systems store faults in an Events history exactly like Carrier Infinity. For the cooling side of a Carrier system, see Carrier AC repair, and the full lineup on our Carrier brand page.