Danfoss Refrigeration Error Codes: A01, E29, E02 and More

On Danfoss ERC 21X controllers, A01 is a high temperature alarm, meaning the air in the cabinet is too warm. E29 means the air temperature sensor is defective or disconnected, and E27 the same for the evaporator sensor. On the ERC 112, E01 to E04 are sensor failures on inputs S1 to S4. On EKC 202D, EKC 302D and AK-CC 210 controllers, A1 is a high temperature alarm and E1 a controller fault.

Danfoss uses different code formats on different controllers, so start by finding the controller's model name. The tables below come from Danfoss's own manuals for each one.

At a glance

Code	Controller	What Danfoss says it means
A01	ERC 21X	High temp alarm: air temperature in cabinet is too high
A02	ERC 21X	Low temp alarm: air temperature in cabinet is too low
E29	ERC 21X	Air temperature sensor is defect or electrical connection is lost
A61	ERC 21X	Condenser temp. too high, check air flow
E01, E02	ERC 112	S1 or S2 sensor failure
A1	EKC, AK-CC 210	High temperature alarm
E1	EKC, AK-CC 210	Faults in the controller

Source: Danfoss ERC 21X and ERC 112 user guides, and the EKC 202D/302D and AK-CC 210 manuals.

How Danfoss shows an alarm

On the ERC 21X, Danfoss's controller documentation says the display alternates between the air temperature and the codes of any active alarms, with the alarm bell shown, until the alarm is resolved.

On the EKC 202D, EKC 302D and AK-CC 210, the LEDs on the front flash and the alarm relay activates. Pushing the top button shows the alarm report, and pushing again scrolls through several. Danfoss explains a useful difference between the two kinds of code: A alarms only appear once a set time delay has passed, while E alarms appear the moment the error occurs, and an A alarm stays hidden while an E alarm is active.

ERC 21X codes

Danfoss says the ERC 211, 213 and 214 are typically used in glass door merchandisers, commercial fridges and freezers, and cold rooms.

Code	Alarm	What Danfoss says it means
E29	Sair sensor error	Air temperature sensor is defect or electrical connection is lost
E27	Def sensor error S5	Evaporator sensor is defect or electrical connection is lost
E30	Sc sensor error	Condenser sensor is defect or electrical connection is lost
A01	High temp alarm	Air temperature in cabinet is too high
A02	Low temp alarm	Air temperature in cabinet is too low
A99	High Volt alarm	Supply voltage is too high (compressor protection)
AA1	Low Volt alarm	Supply voltage is too low (compressor protection)
A61	Condenser alarm	Condenser temp. too high, check air flow
A80	Cond. block alarm	Condenser temp. too high, manual reset of alarm required
A04	Door alarm	Door has been open for too long
A15	DI Alarm	External alarm from DI input
A45	Standby Alarm	Control has been stopped by r12 Main switch
Err		The temperature cannot be displayed due to a sensor error

Some displays are messages rather than alarms: Pud means a pull-down cycle has started, Loc and UnL that the keyboard is locked or unlocked, PS that an access code is needed, OFF and On that control has been stopped or started with the main switch, and Fac that the controller has been reset to factory settings.

A01 on a Danfoss controller

A01 is the most searched Danfoss code. It means the cabinet air is warmer than the high alarm limit set in the controller. It is not a fault in itself, but a sign that something has stopped the cabinet holding temperature, such as a door left open, a heavy warm load, a blocked condenser or a fault in the refrigeration system. Check the door and the load first. If A61 or A80 appears alongside it, the condenser is running too hot, and if it returns with the door shut and the cabinet loaded normally, it needs an engineer.

ERC 112 codes

The ERC 112 uses short text codes. These come from Danfoss's ERC 112 user guide.

Code	What Danfoss says it means
Hi	Air temperature is higher than the high alarm limit for the set delay
Lo	Air temperature is lower than the low alarm limit for the set delay
Con	Condenser temperature is too high or too low
dor	Door open for longer than the set time
uHi	Line voltage is higher than the set limit
uLo	Line voltage is lower than the set limit
LEA	Compressor running continuously for longer than the set time
E01	S1 sensor failure
E02	S2 sensor failure
E03	S3 sensor failure
E04	S4 sensor failure

What each sensor does depends on how the controller has been configured, so an engineer will check which probe is on the input in alarm. The ERC 112 also shows status messages that are not faults: dEF for defrosting, Eco for Eco mode, SC for pull-down (super-chill) mode and HoL for holiday mode. unP and Prg mean the device is unprogrammed or has not finished programming, and its relay output stays locked until it is.

EKC 202D, EKC 302D and AK-CC 210 codes

These controllers share one alarm list, from Danfoss's EKC 202D and 302D manual and its AK-CC 210 user guide.

Code	What Danfoss says it means
A1	High temperature alarm
A2	Low temperature alarm
A4	Door alarm
A5	Information. Parameter o16 is expired (maximum hold time)
A15, A16	Alarm. Signal from DI1 or DI2 input
A45	Standby position (stopped refrigeration via r12 or DI input)
A59	Case cleaning. Signal from DI1 or DI2 input
A60	High-temperature alarm for the HACCP function (AK-CC 210)
E1	Faults in the controller
E6	Fault in real-time clock. Check the battery or reset the clock (EKC 202). Reset the clock (EKC 302)
E25	Sensor error on S3
E26	Sensor error on S4
E27	Sensor error on S5
-d-	Defrost in progress, or first cooling after defrost
non	The defrost temperature cannot be displayed. Defrost stops on time

On the EKC, Danfoss says that if the signal from a defined S3 or S4 sensor is lost, emergency cooling takes over and regulation continues using a recorded average cut-in frequency. That keeps the case cold for a while, but not under proper control. Danfoss also notes that -d- can stay on the display for up to 15 minutes after cooling resumes following a defrost, which is normal.

E0, E1, E2 and E8

Older lists of Danfoss codes often include E0, E2 and E8 as sensor faults. These codes do not appear in any of the four Danfoss manuals we checked. E1 does, but on the EKC and AK-CC 210 it means a fault in the controller itself, not a sensor. On the ERC 112, the sensor faults are E01 to E04, with a zero, which is easy to misread as E1 or E2.

How to acknowledge and reset a Danfoss alarm

• ERC 112. Danfoss's user guide says the display flashes the alarm message, and pressing any button acknowledges it.
• EKC and AK-CC 210. A short push on the upper button cuts out the alarm relay and shows the alarm code. Several alarms sit in a rolling list, which the uppermost or lowermost button scrolls through.
• ERC 21X A80. The condenser block alarm needs a manual reset, which Danfoss says can be done by setting r12 Main switch off and on again, or by powering the controller down.

Acknowledging an alarm silences it but does not fix the cause. Most temperature and sensor alarms clear once the condition does.

What you can check safely

• The door. A01, A1, Hi and the door alarms often follow a door left open or not closing properly.
• The condenser. With A61, A80 or Con, Danfoss's advice is to check the air flow and clean the condenser.
• The load. Make sure the cabinet is not overloaded with warm stock and that the air can circulate.
• Standby. A45 means control has been stopped by the main switch setting or a digital input, so check nobody has switched the controller to standby.
• The compressor. Danfoss's ERC 112 guide notes that a compressor that will not start may simply be waiting on its delay timer or a defrost, or seeing a supply voltage that is too low or too high.

Safety

Danfoss's ERC 112 guide warns that the inputs are not galvanically isolated and are connected directly to the mains supply, so door switches, sensors and their cables must meet reinforced insulation requirements. That is a good reason to leave sensor and wiring work to an engineer. Danfoss also warns that resetting to factory settings overwrites the original settings, which on a configured controller can change how the cabinet runs. Work on the refrigerant circuit needs an engineer with the F gas qualifications set out by GOV.UK.

When to call an engineer

• Any sensor error: E27, E29 or E30 on the ERC 21X, E01 to E04 on the ERC 112, or E25 to E27 on the EKC.
• E1 on an EKC or AK-CC 210, which points to the controller itself.
• A80, or A61 that returns after the condenser has been cleaned.
• A01 or A1 that returns with the door shut and a normal load.
• Repeated high or low voltage alarms, which may point to the supply.

Our commercial refrigeration repair team works on Danfoss-controlled cabinets, counters and cold rooms across London. If a cabinet is running but not cold, our guide to commercial fridges that stop cooling covers the usual causes.

Questions people ask about Danfoss error codes

What does A01 mean on a Danfoss controller?

On the ERC 21X, A01 is a high temperature alarm: the air temperature in the cabinet is too high. Check the door, the load and the condenser. If it keeps returning, the refrigeration system needs an engineer.

What is error E29 on a Danfoss?

E29 on the ERC 21X is an air temperature sensor error. Danfoss says the sensor is defective or its electrical connection has been lost, so the controller cannot read the cabinet temperature. It needs an engineer.

What does E02 mean on a Danfoss ERC 112?

E02 is a failure of the sensor on input S2. The display blinks E02, and if configured, the alarm relay cuts in and the buzzer sounds. What that sensor measures depends on how the controller is set up.

What does E1 mean on a Danfoss controller?

On the EKC 202D, EKC 302D and AK-CC 210, E1 means faults in the controller itself, not a sensor fault. On the ERC 112, the equivalent sensor code is E01, which is the S1 sensor.

What does A45 mean on a Danfoss?

A45 is a standby alarm. Refrigeration has been stopped through the r12 main switch setting or a digital input, so the cabinet is not cooling because it has been told to stop, not because of a fault.

How do I reset a Danfoss alarm?

Press any button on an ERC 112, or give the upper button a short push on an EKC or AK-CC 210, to acknowledge it. Most alarms clear when the cause does. The ERC 21X condenser block alarm A80 needs the main switch setting cycling off and on, or the power cycling.

Keeping a Danfoss cabinet on temperature

Find the controller model, read the code against the right table, and check the door, load and condenser first. Sensor faults and repeat alarms need an engineer, and planned refrigeration maintenance keeps condensers clean and sensors checked before they trigger an alarm.

Last updated: 4 November 2026