Trane Air Conditioner Error Codes — Meanings, Causes & Repair in Greater Vancouver

Seeing a fault code on your Trane air conditioner? This guide explains what the most common Trane air conditioner error codes mean, what’s safe to check yourself, and when to call HeatLand’s licensed HVAC technicians for Trane air conditioner repair across Metro Vancouver and the Fraser Valley.

The codes below apply across common Trane models (ComfortLink II, XV, XR). Meanings follow Trane’s documented fault codes — always confirm against your unit’s own manual, because exact wording can vary by model, control board and firmware.

How to read Trane air conditioner error codes

Trane communicating systems (XV20i, XV18, XR17, etc.) use the ComfortLink II control bus. Faults are reported as numeric Alert Codes that appear on the ComfortLink II color thermostat (XL824/XL850/XL950/XL1050) as 'Err ###' or 'Error ###.##', and on the outdoor unit's CDA (Charge Diagnostic Assistant) board as red Fault-LED flash patterns. Each numeric Alert Code corresponds to a CL2.xxx.xx alarm ID in Trane service literature (e.g. Alert 79 = CL2.079, Alert 80 = CL2.080). The 4 highest-priority faults flash sequentially on the LED; cycle power to the outdoor unit to clear stored faults. Single-stage, non-communicating Trane ACs (basic XR models) have no digital code display and instead show a hard-wired condenser-board status LED only. Source: Trane Service Facts 'ComfortLink II System Heat Pump' D802247P01 Rev08 (4TWZ0060) and Trane/American Standard CL2 Alert Code reference.

Trane air conditioner error codes & what they mean

These are the Trane air conditioner codes our Greater Vancouver technicians see most. Anything marked pro repair involves electrical, refrigerant, sensor or control-board work that must be done by a licensed HVAC technician — never open the indoor/outdoor unit or refrigerant lines yourself.

Code	What it usually means	Common causes	Safe to check yourself
18	24V Sensing Error / Control Fault. 24V is not being sensed at the Y1 input (J1 connector) of the outdoor control board, or the outdoor control board has an internal failure (CTRL FLT / AC Sns Err). Displayed as Err 18; CDA LED shows 18 flashes pro repair	Missing or faulty Y1 (red wire) 24VAC signal reaching the outdoor control board; Loose or corroded low-voltage wiring at the outdoor unit J1 connector; Internal failure of the outdoor control/inverter board, sometimes from a line-voltage spike or static discharge	Confirm the thermostat is set to Cool with the setpoint below room temperature; Check that the outdoor disconnect and the breaker for the air conditioner are both ON; Try one power cycle: turn the AC breaker off, wait one minute, turn it back on, and allow several minutes for the system to re-establish
50	Duplicate Outdoor Temperature Sensor. Two outdoor temperature sensors are reporting on the same system (configuration conflict). CDA LED shows 15 flashes pro repair	Both an internal ambient sensor and an external outdoor temperature sensor configured/wired at the same time; Outdoor temperature sensor wiring or configuration error	Try one power cycle of the air conditioner at the breaker and wait several minutes
67	Temperature Sensor Fault – out of range (open or shorted). Covers the outdoor Ambient, Coil, Liquid, or External Outdoor Temperature sensor depending on sub-code. Displayed as Err 67; CDA LED shows 5, 6, 11, or 13 flashes depending on which sensor pro repair	Outdoor ambient, coil, liquid, or outdoor-temperature sensor open, shorted, or out of range; Damaged sensor wiring or loose sensor connector on the outdoor control board; Failed temperature sensor (thermistor)	Try one power cycle of the air conditioner at the breaker and allow several minutes to clear
68	Defrost Fault (heat pump models only). Defrost Fault A, B, and/or C detected. CDA LED shows 2, 3, or 4 flashes. (Cooling-only air conditioners do not run defrost.) pro repair	Heat-pump defrost sensor fault, low refrigerant charge, shorted coil sensor, or open ambient sensor (heat pump only); Defrost terminated on time-override or high delta-T	For heat pumps, confirm the outdoor coil is not blocked by ice, snow, leaves, or debris and clear anything obstructing airflow around the unit; Try one power cycle at the breaker
79	Low Pressure Cut-Out (LPCO) Fault. The low-pressure switch has opened. Sub-codes cover a short lockout, a heat/cool lockout, and a hard lockout (opened a third time – cycle power to reset). In cooling, suction pressure has dropped below the low-pressure limit. Displayed as Err 79; CDA LED shows 7 flashes pro repair	System low on refrigerant charge (leak); Indoor airflow restriction in cooling (dirty filter, blocked return, dirty indoor coil); Low-pressure switch wiring open or shorted	Replace or clean the indoor air filter if dirty; Make sure supply and return vents are open and unobstructed; Confirm thermostat is set to Cool below room temperature
80	High Pressure Monitor Fault. The high-pressure switch (HPCO, limit approximately 650 psig) has tripped. Sub-codes cover a short lockout, a hard lockout after 6 short-lockout events, and reduced-capacity operation. Displayed as Err 80; CDA LED shows 17 flashes pro repair	Refrigerant overcharge; Outdoor fan failure or restricted outdoor (condenser) airflow – dirty or blocked condenser coil, recirculating hot air; Non-condensables in the refrigerant	Clear leaves, grass, dirt, and debris from around and on the outdoor condenser so air flows freely (do not open the unit); Make sure nothing is blocking airflow within about two feet of the outdoor unit; Replace a dirty indoor air filter and keep vents open
90	Excessive Communication Errors / Loss of Heat-Cool Demand Message (COMM). The ComfortLink II control bus has too many communication errors or lost the demand message. The thermostat is no longer reliably talking to the outdoor unit. CDA LED shows 1 flash (with code 91) pro repair	Loose, open, shorted, or reversed-polarity communicating-bus wiring (the D and B / 1-2-3-4 data leads); Voltage out of range on the data line (12VDC indicates good communication; ~16VDC indicates a loss of communication); Failed control board on an indoor or outdoor component	Power-cycle both the thermostat and the equipment: turn the system off at the breakers, wait one minute, restore power, and give the system a few minutes to re-establish communication
91	Loss of Bit Master / Clock Signal (COMM). The communicating system lost the master clock/bit-master signal on the ComfortLink II bus. Displayed as Err 91; CDA LED shows 1 flash pro repair	Communicating-bus wiring fault (open, shorted, or reversed); Failed master control on the bus	Power-cycle the system at the breakers, wait one minute, and allow a few minutes to re-establish communication
89	Equipment Missing / Configuration Fault (Config Fault). Equipment that was auto-discovered at startup is no longer reporting on the communication bus – the thermostat expected a component (such as the outdoor unit) and can no longer find it pro repair	Loss of communication to the outdoor unit or another component (open/shorted data line, ~16VDC on the bus instead of 12VDC); A breaker tripped or power lost to one piece of equipment; Loose communicating-bus connection at a component	Verify the breaker and disconnect for the outdoor unit are ON; Power-cycle the system at the breakers, wait one minute, and allow it to re-discover equipment
102	Y2 without Y1 – Miswire (24-volt mode only). A second-stage cooling call (Y2) is present without the first-stage call (Y1), indicating reversed or incorrect field wiring. CDA LED shows 10 flashes pro repair	Y1 and Y2 field control wires reversed or miswired at the outdoor unit	This is a wiring/installation fault – no safe homeowner check beyond confirming the thermostat is set to Cool; contact a licensed technician
113	Liquid Pressure Sensor Fault – out of range (open or shorted). The liquid-line pressure transducer reading is invalid. Displayed as Err 113; CDA LED shows 12 flashes pro repair	Liquid-line pressure transducer open, shorted, or out of range; Transducer wiring or connector fault at the outdoor control board	Try one power cycle of the air conditioner at the breaker and allow several minutes
114	Personality Module (PM) Error. The PM (configuration module on the outdoor control board) is missing or contains bad data. Operational sub-codes continue running; non-operational sub-codes stop the compressor until a good PM is inserted. Displayed as Err 114; CDA LED shows 14 flashes pro repair	Personality Module missing, unseated, or corrupted on the outdoor control board; Damaged or incorrect PM after a board service	Try one power cycle at the breaker; if the code persists this requires service
123	Demand Configuration Fault. The system received a demand/configuration that does not match its stored setup. CDA LED shows 16 flashes pro repair	Configuration mismatch between the thermostat and the outdoor unit after equipment change or setup; Communicating-bus configuration error	Power-cycle the system at the breakers and allow it to re-establish configuration
126	Equipment Change / Thermostat communication fault (ComfortLink II XL950/XL1050). The thermostat detects that the equipment it discovered no longer matches what is reported on the bus, or it has lost communication with the HVAC equipment. Shown as Err 126 / Error 126 on the ComfortLink II display pro repair	Communication fault between the ComfortLink II thermostat and the indoor/outdoor equipment; Loose, corroded, or reversed communicating-bus (data) wiring; A component lost power or was changed without being re-discovered	Check the thermostat is seated firmly on its base; Power-cycle the system at the breakers and disconnect, wait about one minute, restore power, and allow a few minutes to re-establish communication
EEV 1 Flash	Electronic Expansion Valve (EEV) coil open or intermittent short – replace coil. (EEV board red Fault LED, heat-pump models with EEV. The EEV is bypassed in cooling mode, so EEV faults primarily affect heating performance.) pro repair	Open or shorted EEV motor coil; EEV wiring/connector fault	Try one power cycle at the breaker (EEV faults 1-5 clear with a power cycle)
EEV 3 Flash	Suction Pressure Transducer input out of range – replace transducer. (EEV board red Fault LED; valve closes and the low-pressure cut-out will trip.) pro repair	Suction pressure transducer open, shorted, or out of range; Transducer wiring fault	Try one power cycle at the breaker
EEV 7 Flash	EEV is responding but the system is not performing properly – typically low refrigerant charge or a restriction. (EEV board red Fault LED.) pro repair	Low refrigerant charge (leak); Refrigerant-side restriction in the system	Replace a dirty air filter and confirm vents are open; Clear debris from the outdoor unit; then a single power cycle at the breaker

Trane air conditioner codes we get called for most

18 — 24V Sensing Error / Control Fault. 24V is not being sensed at the Y1 input (J1 connector) of the outdoor control board, or the outdoor control board has an internal failure (CTRL FLT / AC Sns Err). Displayed as Err 18; CDA LED shows 18 flashes

Typical causes include missing or faulty y1 (red wire) 24vac signal reaching the outdoor control board; loose or corroded low-voltage wiring at the outdoor unit j1 connector; internal failure of the outdoor control/inverter board, sometimes from a line-voltage spike or static discharge. A few things are safe to check yourself (Confirm the thermostat is set to Cool with the setpoint below room temperature; Check that the outdoor disconnect and the breaker for the air conditioner are both ON), but the repair is a licensed HVAC technician job. HeatLand diagnoses and fixes 18 on Trane air conditioners throughout Greater Vancouver.

50 — Duplicate Outdoor Temperature Sensor. Two outdoor temperature sensors are reporting on the same system (configuration conflict). CDA LED shows 15 flashes

Typical causes include both an internal ambient sensor and an external outdoor temperature sensor configured/wired at the same time; outdoor temperature sensor wiring or configuration error. A few things are safe to check yourself (Try one power cycle of the air conditioner at the breaker and wait several minutes), but the repair is a licensed HVAC technician job. HeatLand diagnoses and fixes 50 on Trane air conditioners throughout Greater Vancouver.

89 — Equipment Missing / Configuration Fault (Config Fault). Equipment that was auto-discovered at startup is no longer reporting on the communication bus – the thermostat expected a component (such as the outdoor unit) and can no longer find it

Typical causes include loss of communication to the outdoor unit or another component (open/shorted data line, ~16vdc on the bus instead of 12vdc); a breaker tripped or power lost to one piece of equipment; loose communicating-bus connection at a component. A few things are safe to check yourself (Verify the breaker and disconnect for the outdoor unit are ON; Power-cycle the system at the breakers, wait one minute, and allow it to re-discover equipment), but the repair is a licensed HVAC technician job. HeatLand diagnoses and fixes 89 on Trane air conditioners throughout Greater Vancouver.

79 — Low Pressure Cut-Out (LPCO) Fault. The low-pressure switch has opened. Sub-codes cover a short lockout, a heat/cool lockout, and a hard lockout (opened a third time – cycle power to reset). In cooling, suction pressure has dropped below the low-pressure limit. Displayed as Err 79; CDA LED shows 7 flashes

Typical causes include system low on refrigerant charge (leak); indoor airflow restriction in cooling (dirty filter, blocked return, dirty indoor coil); low-pressure switch wiring open or shorted. A few things are safe to check yourself (Replace or clean the indoor air filter if dirty; Make sure supply and return vents are open and unobstructed), but the repair is a licensed HVAC technician job. HeatLand diagnoses and fixes 79 on Trane air conditioners throughout Greater Vancouver.

Is it safe to keep running a Trane air conditioner with a fault code?

Most Trane fault codes put the air conditioner into a safe lockout for a reason. You can safely check the basics — the power and breaker on, the air filter clean, the outdoor condenser clear of debris, and the thermostat set to cool — and restart it once. If the code returns, stop and book a technician. Air-conditioner faults are electrical and refrigerant issues — never open the unit or touch the wiring or refrigerant lines yourself.

Trane air conditioner repair across Greater Vancouver

HeatLand has kept Metro Vancouver homes comfortable since 1999. Our licensed, insured technicians diagnose and repair Trane air conditioners — sensor and thermistor errors, communication faults, fan and compressor problems, refrigerant and pressure faults, and control-board issues — including units we didn’t install. We’re brand-agnostic, carry common parts, and give you an honest repair-or-replace assessment with upfront pricing and a free estimate. If your air conditioner is beyond economical repair, we’ll show you right-sized, high-efficiency replacement options and the rebates available.

Need it sorted fast? We offer priority emergency air conditioner repair. Explore Air Conditioner services, browse all air conditioner error codes by brand, or request a free estimate.

Trane air conditioner service areas

We repair Trane air conditioners across Greater Vancouver and the Fraser Valley, including:

Trane air conditioner error code FAQs

Can I reset my Trane air conditioner myself?

Yes — power-cycling the unit at the breaker once is generally safe after you’ve checked the basics (the power and breaker on, the air filter clean, the outdoor condenser clear of debris, and the thermostat set to cool). If the air conditioner faults again right away, stop and note the code — repeatedly resetting a air conditioner that keeps locking out can mask a real problem. Call a licensed HVAC technician to diagnose it.

What does the Trane 50 code mean?

On Trane air conditioners, 50 commonly indicates duplicate outdoor temperature sensor. two outdoor temperature sensors are reporting on the same system (configuration conflict). cda led shows 15 flashes. Confirm the exact meaning against your unit’s manual — codes can vary by model and series — and have the repair done by a licensed HVAC technician. HeatLand fixes this across Greater Vancouver.

Do you repair Trane air conditioners you didn’t install?

Yes. HeatLand is brand-agnostic and services Trane air conditioners throughout Metro Vancouver and the Fraser Valley, whether or not we installed the unit. We carry common parts and give you an honest repair-or-replace assessment.

Is a Trane air conditioner fault code an emergency?

No heat in cold weather or no cooling in a heat wave is worth treating urgently. For priority air conditioner repair across Greater Vancouver, call (604) 330-3812.

How much does Trane air conditioner repair cost in Vancouver?

It depends on the fault. Many Trane codes point to sensors, thermistors, capacitors or control parts — usually far cheaper than replacement. We give upfront pricing and a free estimate before any work.

More Air Conditioner error-code guides

HeatLand repairs every major air conditioner brand across Greater Vancouver. More brand guides: