True Refrigerator Error Code dOr / HI / LO: Door and Temperature Alarms
On a True cabinet with a Carel control, dOr is the open door alarm, HI is the high temperature alarm and LO is the low temperature alarm. They are warnings and the cabinet keeps running. Judge the food with a thermometer, not the display, and call us if HI or LO keeps coming back.
Medium: these are warnings and the cabinet runs, but food can warm or freeze if HI or LO continues.
- Code
- DOr / HI / LO
- Maker
- True
- Equipment
- Reach-in refrigerators
- Applies to
- Carel control
What does True error code DOr / HI / LO mean?
These three Carel messages are alarms, not breakdowns. The control compares door status and cabinet air temperature with its set limits and raises a warning when one is crossed. DOr appears when the door has stayed open too long and usually clears as soon as it shuts. HI says the box is warmer than its high limit, which points to heat getting in or not leaving: a hot load, a dirty condenser or a stalled fan. LO says the cabinet is colder than its low limit, so food near the evaporator may start to freeze. Because the cabinet continues to run, the real question is whether the product is staying at a safe temperature. A thermometer placed in the food answers that better than the display does, especially if a probe reads off and LO shows while the food is not actually cold.
Affected models and control systems
True cabinets with a Carel control. The three messages belong to the same display code list.
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
- DOr lit while a door is open
- HI shown with a warm cabinet
- LO shown with frozen lettuce or drinks
- An alarm tone that stops when the door closes
Possible causes
Listed in True's documentation
- A door held open or a leaking gasket at the Carel cabinet
- A heat-loaded or dirty condenser that lets the cabinet warm up and trip HI
- A stalled evaporator or condenser fan that stops air from moving
- A cabinet probe that reads off, so LO appears while food is not cold
Other likely causes — what usually sits behind error code DOr / HI / LO on this control. A technician confirms which one it is before any part is replaced.
- A condenser filter clogged with kitchen grease that raises head temperature
- A set point nudged colder, so LO shows with normal loading
- A door ajar behind a rack that the crew cannot see
Safe checks before calling for service
- Close the door and wait a few minutes to see whether dOr clears.
- Use a thermometer in the food, not the display, to judge the cabinet.
- Clear dust from around the condenser.
- Move food if the cabinet is out of range.
- If HI or LO returns, note which one and the thermometer reading.
How a technician diagnoses error code DOr / HI / LO
- Confirm which alarm is active and when it started.
- Compare the display with a calibrated thermometer in the cabinet.
- Check the gasket, door fit and door switch.
- Inspect the condenser coil, condenser fan and evaporator fan for blockage and operation.
- Test the cabinet probe resistance against a reference.
- Review set point and alarm limits before replacing any part.
- Checking fans and the condenser means working beside live line-voltage wiring behind panels.
- An HI alarm that traces to the sealed system needs gauges and EPA-certified refrigerant handling.
- Probe testing needs a meter and a known reference temperature.
Technical reference
- Document
- Commercial Refrigeration General Control Guide TEC_TM_001 Rev C, Carel p.75 Display Code Definitions
- Edition
- TEC_TM_001 | REV. C | EN, 09/3/2025, P#811072
- Models / control
- Carel control
- 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 the cabinet broken when HI shows?
Not necessarily. It is a warning that the box is warmer than its limit; check the food and look for blocked air or an open door.
Will dOr clear by itself?
Yes, normally as soon as the door shuts.
Why would LO show when the food is not cold?
A probe reading low can trigger it, which is why a separate thermometer is the better guide.
Need help with True error code DOr / HI / LO?
A technician confirms the cause on site and gives you the price in writing before any work starts.