True Refrigerator Display dEF / deF / dF: Defrost in Progress
DEF, deF and dF all say that your True cabinet is in a defrost cycle, which is normal. Wait for it to clear and avoid opening the door more than needed. If it stays on for hours, call us to check the probe, heater or settings.
Low: a normal operating state; the cabinet recovers when defrost ends.
- Code
- DEF / deF / dF
- Maker
- True
- Equipment
- Reach-in refrigerators
- Applies to
- All
What does True error code DEF / deF / dF mean?
DEF, deF and dF are the same message written on different True controls: the cabinet is in a defrost cycle. The control briefly stops cooling so heat can melt frost from the evaporator coil, as on the T-49-HC. Frost builds on the coil as moist air passes it, and unless it is melted off, airflow drops and cabinet temperature climbs. The display may show dEF for a short time after defrost ends while the coil settles. Cabinet temperature can rise a little during this period and then recover, which is normal. The message only becomes a concern if it stays on for hours, which points to a defrost that never ends because of a probe or heater, or if defrosts come too often because of settings. Water that cannot leave the cabinet after defrost, from a blocked drain, is a separate problem that shows as pooling.
Affected models and control systems
True cabinets across the lineup, including the T-49-HC; the spelling depends on the controller.
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
- DEF, deF or dF on the display
- Fans paused and the cabinet briefly not cooling
- A small temperature rise that then recovers
- Water pooling after defrost if the drain is blocked
Possible causes
Listed in True's documentation
- Nothing needs repair if the message clears
- A defrost that never ends, which points to a probe or heater
- A defrost that is too frequent because of settings
- Water pooling after defrost from a blocked drain
Other likely causes — what usually sits behind error code DEF / deF / dF on this control. A technician confirms which one it is before any part is replaced.
- A defrost termination probe that no longer senses the coil warming
- A defrost heater that is weak, so frost melts slowly
- A drain line partly clogged with food debris
Safe checks before calling for service
- Wait for the message to clear on its own.
- Avoid opening the door more than needed during defrost.
- Check that the cabinet temperature recovers within a normal time.
- If dEF stays on for hours, note how long it has been on.
- Tell us whether water is collecting under or inside the cabinet.
How a technician diagnoses error code DEF / deF / dF
- Confirm whether defrost is running long by timing it against the cabinet's settings.
- Check the defrost termination probe and its reading.
- Test the defrost heater with a meter.
- Review the defrost interval and duration settings.
- Clear and flush the drain and check for ice blocking it.
- Replace the probe or heater only after the test shows it failed.
- Defrost heaters run on line voltage inside the evaporator housing.
- A probe that reads wrong can cause a defrost that never ends or one that cuts short.
- Defrost interval and duration are controller settings tied to the cabinet's data.
Technical reference
- Document
- Commercial Refrigeration General Control Guide TEC_TM_001 Rev C, p.110 Display Code Definitions
- Edition
- TEC_TM_001 | REV. C | EN, 09/3/2025, P#811072
- Models / control
- All
- 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
Is dEF an error?
No. It reports a normal defrost cycle.
Why did the temperature go up during dEF?
Cooling pauses so the coil can melt frost. It recovers once defrost ends.
When should I worry?
If dEF stays on for hours or the cabinet does not recover, a probe, heater or setting may be the cause.
Need help with True error code DEF / deF / dF?
A technician confirms the cause on site and gives you the price in writing before any work starts.