True Refrigerator Error Code E4 / E5 / E6: Danfoss ETC Output Problems
E4, E5 and E6 are output problem codes on a True cabinet with a current Danfoss ETC display. E4 points to the compressor, E5 to the heater and E6 to what the control calls a pot problem. Check food temperature, do not open panels, and call us right away if the cabinet is warm.
High: a compressor or heater output problem can stop cooling or defrost and put food at risk quickly.
- Code
- E4 / E5 / E6
- Maker
- True
- Equipment
- Reach-in refrigerators
- Applies to
- Danfoss ETC (current display)
What does True error code E4 / E5 / E6 mean?
E4, E5 and E6 are not temperature alarms. They tell a technician the ETC control has found a problem with something it is switching. E4 points to the compressor output, E5 to the heater output, and E6 to what the control calls a pot problem. When the compressor output is affected, cooling can stop altogether. When the heater output is affected, defrost fails and frost builds. A compressor or heater problem can put food at risk quickly, so the right first move is a thermometer reading and a decision about moving perishables. The cause can sit in the wiring to the load, the relay or output on the control, the compressor start parts, or the heater element and its connection. Which code you see decides where the technician starts.
Affected models and control systems
True cabinets with a current Danfoss ETC display. E4 is compressor, E5 heater, E6 pot problem.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- E4, E5 or E6 on the display
- Compressor not running and the cabinet warming
- Frost building because defrost is not running
- Warm product within hours
Possible causes
Listed in True's documentation
- Wiring to the compressor or heater
- The relay or output on the control
- The compressor start parts
- Heater element or its connection
Other likely causes — what usually sits behind error code E4 / E5 / E6 on this control. A technician confirms which one it is before any part is replaced.
- A compressor start relay or capacitor wearing out and tripping the output
- A heater element open from long use
- A wire at a terminal loosened by compressor vibration
Safe checks before calling for service
- Write down which of the three codes shows.
- A thermometer on the top shelf shows quickly whether food is still cold.
- Do not open panels or touch wiring.
- If the cabinet is warm, move perishable food to another cooler and call us.
- Tell us whether you can hear the compressor running.
How a technician diagnoses error code E4 / E5 / E6
- Read the code and confirm cabinet temperature.
- Check supply voltage to the cabinet.
- Test the compressor circuit, start parts and windings with a meter.
- Test the heater element resistance and its wiring.
- Check the relay or output on the ETC control.
- Replace the failed load or control only after the tests.
- The compressor and heater circuits carry full line voltage and need proper meter testing.
- Compressor start parts can hold a charge and are only handled by someone trained.
- If the compressor is failing, the sealed system needs EPA-certified work.
Technical reference
- Document
- Commercial Refrigeration General Control Guide TEC_TM_001 Rev C, Danfoss ETC p.88 Display Code Definitions
- Edition
- TEC_TM_001 | REV. C | EN, 09/3/2025, P#811072
- Models / control
- Danfoss ETC (current display)
- Section
- Electronic Control (with Display) - Display Code Definitions: Carel p. 74, Danfoss ERC/ETC p. 87, Dixell p. 96, LAE p. 110
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related True reach-in refrigerator error codes
Are E4, E5 and E6 temperature alarms?
No. They report a problem with an output the control switches, not the cabinet temperature.
What does E6 mean?
The control calls it a pot problem. Tell us the code and we will check what it switches on that cabinet.
Is it urgent?
Yes if the cabinet is warming, since a compressor problem can spoil food within hours.
Need help with True error code E4 / E5 / E6?
A technician confirms the cause on site and gives you the price in writing before any work starts.