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Common error codes on air conditioners, heat pumps, furnaces, & what they mean

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A/C & Heat Pump or Furnace Common Error Codes

Article Contents

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Error codes depend on the brand and model of equipment

Error codes depend on the brand and model of equipment; if you don't have an owners/installation manual that's what you will ultimatelhy need to diagnose the error code displayed at your equipment.

See MANUALS & PARTS GUIDES - HVAC to find the manual and thus a detailed error code guide for your system.

But fortunately there are some common error codes used by many heating and air conditioning equipment manufacturers. We give those here along with suggestions for finding the manuals and error codes for your specific air conditioner or heater in the tables given below.

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Common Cnn Error Codes

See

LG HVAC SYSTEMS MANUALS & ERROR CODES  for a list of Cnn or CHnn error codes and their meanings

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Common Enn Error Codes

E1 error code

air filter is dirty and needs cleaning or replacement.

E4 Error code

on a split system A/C or heat pump unit tells you that the sytem is going into defrost mode and will or may stop cooling for an interval.

Defrost mode and the E4 code is not an error, it's a normal operating condition.

If your system is going into defrost mode too often or when it shouldn't or isn't needed then a temperature sensor may need replacement.

E5 Error code

E5 on a split system A/C unit and some other systems using a condensate reservoir means that a condensate collection tank is full and needs to be emptied.

For example, LG HVAC system error codes provided by that company tell us:

E5 Error code indicates that the water collection tank is full. To drain the water collection tank completely, leave the bottom drain cap off long enough to allow any residual water to drain out. Once the water tank is completely drained and no more water flows out, reinstall the cap.

Watch out: if you don't empty the water/condensate tank your system will either shut down or you risk a leak and water damage to your building.

LG's error codes are used by some other companies too.

E12 Error Code

An E12 error code means that the system is seeing a call for heat but heat is not being delivered.

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Carrier HVAC Error Codes

Carrier Air Handler Blower Unit Codes

E0 Indoor unit EEPROM parameter error
E1 Indoor / outdoor units communication error
E3 Indoor fan speed has been out of control
E4 Indoor room temperature sensor T1 open circuit or short circuit
E5 Evaporator coil temperature sensor T2 open circuit or short circuit
EC Refrigerant Leakage Detection
F1 Outdoor ambient temperature sensor T4 open circuit or short circuit
F2 Condenser coil temperature sensor T3 open circuit or short circuit
F3 Compressor discharge temperature sensor T5 open circuit or short circuit
F4 Outdoor unit EEPROM parameter error
F5 Outdoor fan speed has been out of control
P0 IPM malfunction or IGBT over-strong current protection
P1 Over voltage or over low voltage protection
P2 High temperature protection of compressor top diagnosis and solution
P4 Inverter compressor drive error
P5 Mode conflict
P6 Compressor voltage protection

Carrier Outdoor Compressor/Condenser Unit Error Codes

E0 Outdoor EEPROM malfunction
E2 Indoor/outdoor units communication error
E3 Communication malfunction between IPM board and outdoor main board
E4 Open or short circuit of outdoor unit temperature sensor
E5 Voltage protection
E8 Outdoor fan speed malfunction
F1 No A Indoor unit coil outlet temperature sensor or connector of sensor is defective
F2 No B Indoor unit coil outlet temperature sensor or connector of sensor is defective
F3 No C Indoor unit coil outlet temperature sensor or connector of sensor is defective
F4 No D Indoor unit coil outlet temperature sensor or connector of sensor is defective
F5 No E Indoor unit coil outlet temperature sensor or connector of sensor is defective
P1 High pressure protection
P2 Low pressure protection
P3 Current protection of compressor
P4 Temperature protection of compressor
P5 High temperature protection of condenser
P6 IPM module protection

Miscellaneous Carrier HVAC Error Codes

DN Communication error between main board and EXV.
EC Refrigerant leakage detection.
EE Memory card error.
EN Frequency limitation for module circuit protection.
EU Frequency limitation for module temperature protection.
FH Frequency limitation for freeze protection.
H1 Defrost or heating oil return cycle.
H3 Compressor overheat protection.
H5 IPM Protection.
H7 Compressor speed reduction.
HC PFC protection malfunction.
HE Compressor demagnetizing protection.
L9 Compressor high voltage protection.
LC Compressor start-up failure.
LD Compressor phase loss protection.
LE Compressor stalling.
LF Compressor over-speed protection.
LP Indoor and outdoor units mismatch.
PA Input current protection.
PC Current sensor malfunction.
PD Current sensor miss-wiring protection.
PF Inverter board ambient temperature sensor malfunction.
PH High voltage protection.
PL Low voltage protection.
PP Abnormal input AC voltage.
PU Capacitor charging malfunction.

 

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Sharp HVAC Error Codes

1-0 Heat exchanger thermistor short circuit error
1-1 Outdoor temperature thermistor short circuit error
1-2 Suction thermistor short circuit error
1-3 2-way valve thermistor short circuit error
1-4 Heat sink thermistor short circuit error
2-0 Compressor high temperature error
2-1 Compressor discharge overheat
2-2 Outdoor unit heat exchanger overheat
2-3 Indoor unit heat exchanger overheat
2-4 IPM high temperature error
2-5 IPM high temperature error
3-0 Temporary stop due to dehumidifying operation
5-0 Heat exchanger thermistor open circuit error
5-1 Outdoor temperature thermistor open circuit error
5-2 Suction thermistor open circuit error
5-3 2-way valve thermistor open circuit error
5-4 Discharge thermistor open circuit error
5-5 Heat sink thermistor open circuit error
6-0 DC over current error
6-1 IPM pin level error
7-0 AC over current error
7-1 AC current error when OFF
7-2 AC maximum current error
7-3 AC current deficiency error 
9-0 Thermistor installation error or 4-way valve error
9-3 Compressor torque control error
9-4 4 way valve error or Gas leak error 
9-5 2-way valve and 3-way valve close error
9-6 Solenoid valve error
10-0 EEPROM (Outdoor) data error
10-1 EEPROM (Outdoor) data error
10-2 CPU (Outdoor) RAM data error
11-0 Outdoor unit DC fan rotation error
11-1 Outdoor unit DC fan driver IC error
11-2 Outdoor unit DC fan lock error
11-3 Detection error of DC fan negative rotation before compressor is driven 
11-4 Detection error of inverter current for DC fan
11-5 Outdoor unit DC fan open connector error
12-0 Thermal fuse error in terminal board (for power supply)
13-0 Compressor startup error
13-1 Compressor rotation error (At 120°energizing)
13-2 Compressor rotation error (At 180°energizing)
13-3 Detection error of inverter current 
14-0 PAM over voltage error
14-1 PAM clock error
14-2 PAM under voltage error
14-4 PFC Module error
17-0 Serial open-circuit
18-0 Serial short-circuit
18-1 Serial erroneous wiring
18-2 High speed serial communication error
19-0 Indoor unit fan error
20-0 EEPROM data error
20-1 External EEPROM initial data reading error
20-2 External EEPROM verify error
20-3 External EEPROM communication error
21-0 Incomplete closing of louver cover or louver closing lever
22-0 Plasmacluster connecting error
22-1 Lock On Sensor error
22-2 Over time of accumulated plasmacluster operation time
23-0 Wrong connect to 200V AC
24-0 Wireless lan module communication error
24-1 Connecting error with wireless lan router
24-2 Internet condition error
24-3 Connecting error with server
25-1 AC clock error
26-1 Indoor unit room temperature thermistor
26-2 Indoor unit pipe temperature thermistor
26-3 Gas sensor error
26-4 Dust sensor error
28-0 Initial error filter cleaning operation
28-1 Error during filter cleaning operation
28-2 Incomplete closing of open panel or front panel, or air filter installation error 
28-3 Filter detachment error
29-0 Panel cannot open
29-1 Panel cannot close
31-0 or 31-6 or 31-7 Sub microcomputer error

 

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Common Trane HVAC Error Codes

E1 Indoor and Outdoor Unit Communication Error
E2 Room Temperature Sensor Malfunction
E3 Pipe Temperature Sensor Malfunction
E4 Outdoor Temperature Sensor Malfunction
E5 Pump Temperature Sensor Malfunction
E6 Outdoor Unit Malfunction
E7 Electrical Erasable Read-Only Memory (EEPROM) Test Fail
E8 Water-level Alarm Error
EC Refrigerant Leakage Detected
EB Motor Speed Out of Control
ED Outdoor Unit has Low Pressure Error

Common Trane Inverter Unit Error Codes

E1 Indoor and Outdoor Unit Communication Fault Code
E2 Room Temperature Sensor Error
E3 T2 Temperature Sensor Error
E4 T2B Temperature Sensor Error
E7 Electrical Erasable Read-Only Memory (EEPROM) Test Fail
E8 Fan Motor Speed Out of Control
EE Water-level Alarm Malfunction
ED Outdoor Unit Malfunction
EC Refrigerant Leakage Detected
F3 Indoor Twin Rotary Compressor Communication Error
F4 Issues with Twin Rotary Compressor

Trane Split System A/C Heat Pump Error Codes

C5 Preventive System for Jump Wire Cap Malfunction
E1 High-pressure Protection System/PCB Malfunction
E2 Anti-freezing Preventive
E4 Compressor Exhaust Protection from High Temperature
E5 Alternate Current (AC) Overload Protection
E6 Indoor and Outdoor Unit Communication Error
E8 Unit Protection from High Temperature
EU Intelligent Power Module (IPM) Temperature Overload
F1 Ambient Sensor Open/Short circuited (Indoor Unit)
F2 Evaporator Sensor Open/Short circuited (Indoor Unit)
F3 Ambient Sensor Open/Short circuited (Outdoor Unit)
F4 Condenser Sensor Open/Short circuited (Outdoor Unit)
F5 Air Exhaust Sensor Open/Short circuited (Outdoor Unit)
F6 Overload at Limit
F8 Overcurrent Requires Descending Frequency
F9 Air Exhaust Requires Descending Frequency
FH Anti-freezing System at Limit
H6 No Feedback from Indoor Motor
PH DC Voltage Generator
PL Low Direct Current (DC) Bus Voltage Preventive System
U3 Direct Current (DC) Bus Voltage Dips
U7 Four-way Valve Malfunction
U9 Zero-cross Detection for Outdoor Units

Trane Controller Error Codes

B5 Liquid Valve Temperature Sensor Open/Short circuited (Indoor Unit)
B7 Gas Valve Temperature Sensor Open/Short circuited (Indoor Unit)
DN Communication Line Disconnected/Expansion Valve Malfunction
E1 High Pressure Prevention System
E2 Anti-freezing Prevention System
E3 Low Pressure Prevention System
E4 Discharge High Temperature Prevention System
E5 Overcurrent Prevention System; Frequency Decreased
E6 Indoor and Outdoor Unit Communication Error
E7 Running Mode Issue
E8 Overload Prevention System; Frequency Decreased
E9 Water Overflow Error (Indoor Unit)
EN Intelligent Power Module (IPM) Current Prevention System
EU Intelligent Power Module (IPM) Temperature Prevention System
F1 Room Air Temperature Sensor Open/Short circuited
F2 Evaporator Temperature Sensor Open/Short circuited
F3 Ambient Temperature Sensor Open/Short circuited (Outdoor Unit)
F4 Condenser Temperature Sensor Open/Short circuited (Outdoor Unit)
F5 Discharge Temperature Sensor Open/Short circuited
F6 Overload Protection; Frequency Restricted
F8 Current Protection; Frequency Restricted
FO System Charge Shortage/Blockage Prevention/Pump Down
F9 High Discharge Temperature; Frequency Restricted
FH Anti-freezing; Frequency Restricted
H1 Defrosting
H3 Compressor Overheating Preventive
H7 Compressor Desynchronizing
H5 Intelligent Power Module (IPM) Current Protection
H6 Stalled Motor
HE Compressor Demagnetization Protection
HC Power Factor Correction (PFC)
L3 Outdoor Fan1 Error
L9 Overpower Protection
LA Outdoor Fan2 Error
LC Compressor Startup Failure
LD Compressor Phase Loss/Reversal
LE Stalling Compressor
LF Speeding
LP Indoor and Outdoor Units Unmatched
P6 Drive Board Communication Error Codes
P9 Alternate Current (AC) Contactor Error Code
PD Sensor Connection Error Code
PE Temperature Drift Error Code
PF Drive Board Temperature Sensor Error Code
PU Capacitor Charging Error Code
P5 Over Phase Current
P7 Intelligent Power Module (IPM) Temperature Tensor Open/Short Circuited
P8 Intelligent Power Module (IPM) Temperature Protection
PH Direct Current (DC) Bus Over-Voltage
PL Direct Current (DC) Bus Under-Voltage
PP Alternate Current (AC) Input Voltage Error Code
U1 Compressor Phase Current Circuit Error Code
U3 Sensor Connection Error Code
U5 Current Circuit Error Code
U7 4-Way Valve Reversing Error Code
U8 PG Motor Zero-Crossing Protection

 

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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

E4 error code on split system A/C unit

This is an incredible resource, so first up thanks for putting it up, mad props.
I'm not a technician or anything, just a consumer. Our split type AC has been acting up the past couple of years.

First the problem was an E4 error code, which has been occurring for over 4 years now. When you leave the AC in normal cooling mode (approx 23-25deg C) sometimes the AC shows E4 then shuts down. There's no consistent way to monitor as there are days where it just runs fine the whole day, sometimes, it runs for 40-50mins then E4 comes on then shuts it down.

We 'remedied' the problem by leaving the AC in 'dehumidifying' mode where the AC shuts down automatically in set intervals and turns back on with cooling.

Last week, we had our AC cleaned as well as the drain pipe de-scaled/flushed. The technician called the manufacturer about the E4 problem and the support told him it's a thermostat sensor issue. They gave him a part that sticks into the evaporator coils in the room unit.

After that repair/cleaning, the E4 problem went away and the AC was quiet and cool.

However, less than a week after the repair, a new error code appeared (E5 this time) and a new weird symptom came up.

The AC would turn on normally, but after 5 seconds or so, the blower will turn on to its maximum setting without cold air, then shuts down with an E5 code. With this new code, there's no 'remedy' like before as it just keeps the AC off.

We just spent a couple of hundred bucks in repair and cleaning and not sure what to do at this point, is the problem due to the age of the unit (replacement imminent) or is it something less serious? We need to inform our landlord ASAP if replacement is needed as it's really hot here in Singapore during summers.

The AC brand is Fujiair model FC9 I believe. It's quite old, I suppose, it's no longer listed on their website. I'm sure it's at least 5 years old since we've been living here with the same AC for that long.

Thanks a lot. On 2011-07-14 by Dave T -

Reply by (mod) - E4 = defrost mode

Dave T: thanks for the nice comments;

Notes on error codes E4 and E5 are above on this page.

Daniel

 

Question: Air conditioner error code charts & meanings

I have turcott thermopompe and it is running but I don't have heat or cold air and thermostat is flashing 12 what's the problem with it (Oct 10, 2016) Gino Ceravolo said:

Reply: Error code 12

Gino:

The error code 12 on some HVAC systems says you're calling for heat and not getting it: I suspect a failed fan limit switch or limit control.

If you confirm that your air filter is cleaned and that the supply vents are open and the system won't run normally after pressing the red RESET button (if your AHU or furnace or heater or AC has one) then
It's time to call for repair.

 

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