Nor-Lake LogiTemp Walk-In Error Code dtt: Defrost Ended on Time
Dtt appears when defrost ended on time instead of on temperature for two defrosts in a row. If the coil sensor never reaches its target, the timer cuts defrost off, which can leave ice on the coil. Keep the door closed, read the box temperature on a hand thermometer, do not chip ice and call us.
Medium: ice can build on the coil and the box may warm if the cause is left alone.
- Code
- Dtt
- Maker
- Nor-Lake
- Equipment
- Walk-in coolers & freezers
- Applies to
- LogiTemp / KE2 Evap OEM (Split-Pak systems, A1 refrigerants)
What does Nor-Lake error code Dtt mean?
A normal defrost on a Nor-Lake Split-Pak walk-in stops when the coil sensor shows the coil is warm enough. A timer is also set as a backstop, so defrost cannot run forever. When the sensor never gets to the termination temperature, the timer cuts the defrost off. One such event can happen, but when defrost ends on time instead of on temperature for two defrosts in a row, the LogiTemp controller shows dtt. The display warns that the coil may still be iced. Ice left on the coil blocks airflow, so the box may run warmer as the evaporator loses its ability to move cold air. The reasons run from the coil sensor reading during defrost, to the defrost heaters or hot gas valve, depending on the system, to ice left from earlier defrosts, to the defrost time and termination settings. Because it takes two cycles to trigger, dtt tells a technician that the problem repeats and is not a one-time glitch.
Affected models and control systems
This applies to the LogiTemp controller on Nor-Lake walk-in coolers and freezers with a Split-Pak system. Heater or hot gas defrost depends on the installation.
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
- Dtt on the display
- Ice or frost still on the coil after a defrost
- Box running warmer between defrosts
- Water or ice at the drain pan
Possible causes
Listed in Nor-Lake's documentation
- Coil sensor reading too low during defrost
- Defrost heaters or hot gas valve not delivering heat
- Ice left from earlier defrosts
- Defrost time and termination settings
Other likely causes — what usually sits behind error code Dtt on this control. A technician confirms which one it is before any part is replaced.
- Heater element burned out in one section of the coil
- Coil sensor sitting where cold air bypasses the heat, so it never warms
- Drain line frozen so melt water refreezes under the coil
Safe checks before calling for service
- Keep the walk-in door closed and the strip curtain in place.
- Look at the gasket and the door sweep for gaps.
- Read the air temperature inside the box on a hand thermometer.
- Do not chip ice off the coil. Call us to schedule service and mention that dtt appeared.
How a technician diagnoses error code Dtt
- Read dtt and the defrost history and settings.
- Inspect the coil for ice and the drain line for freezing.
- Check the coil sensor reading during a manual defrost.
- Test the defrost heaters or hot gas valve with a meter or gauges.
- Verify the time and termination settings, then confirm defrost ends on temperature.
- Defrost heaters run on high line voltage and sit inside the evaporator housing.
- A hot gas defrost involves the refrigerant circuit, which needs gauges and certification.
- Defrost settings affect energy use and box temperature and need the system's setup data.
How error code Dtt differs from similar codes
EdF reports defrosts that start too often, while dtt reports defrosts that end by the timer. They are neighboring problems on the same coil.
Technical reference
- Document
- LogiTemp Electronic Controller System Operations Manual (171527 Rev. A), Alarms & Notifications List pp. 47-51
- Edition
- 171527 Rev. A, 2025 (Refrigerated Solutions Group)
- Models / control
- LogiTemp / KE2 Evap OEM (Split-Pak systems, A1 refrigerants)
- Section
- Alarms & Notifications List, printed pp. 48-52; Troubleshooting Tables from p. 52
- 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 Nor-Lake walk-in cooler & freezer error codes
Does dtt mean no defrost happens?
No. Defrost runs, but the timer ends it before the coil sensor reaches temperature.
Will it correct itself?
Not if the heater or sensor is the cause. Ice will keep building.
Can I melt the ice with hot water?
Please don't. Water adds ice and can damage the coil. Call us.
Need help with Nor-Lake error code Dtt?
A technician confirms the cause on site and gives you the price in writing before any work starts.