True Refrigerator Error Code uHi / uLo: Danfoss ERC Voltage Alarm
UHi and uLo are the high and low voltage alarms on a True cabinet with a Danfoss ERC control. The supply voltage is outside the range the compressor and fans can accept. Check the plug, make sure the cabinet is on its own circuit, and judge the food with a thermometer.
Medium: bad supply voltage can stop the compressor and stress the motors.
- Code
- UHi / uLo
- Maker
- True
- Equipment
- Reach-in refrigerators
- Applies to
- Danfoss ERC
What does True error code UHi / uLo mean?
The ERC control measures the supply voltage and warns you when it is outside the range the compressor and fan motors can accept. UHi means the voltage is too high and uLo means it is too low. Low or high voltage stresses the compressor and fan motors, and it often shows up after outages, storms or when many loads switch on together. The cabinet may shut off its compressor until the voltage returns to a safe range, which means food can warm while the alarm is active. The voltage problem is usually outside the cabinet: the outlet, the breaker, a circuit shared with other equipment, or a loose connection at the plug. A technician measures the voltage at the outlet and at the cabinet, then checks the control's own voltage reading.
Affected models and control systems
True cabinets with a Danfoss ERC control.
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
- UHi or uLo on the display
- Compressor not starting
- Lights or fans behaving oddly
- Alarm that appears when other equipment starts
Possible causes
Listed in True's documentation
- Supply voltage at the outlet or breaker
- Overloaded circuit shared with other equipment
- A loose connection at the plug or outlet
- The voltage measurement on the control
Other likely causes — what usually sits behind error code UHi / uLo on this control. A technician confirms which one it is before any part is replaced.
- A long extension cord or undersized supply that drops voltage under load
- A neighboring circuit with a heavy motor that sags the supply when it starts
- A worn outlet that heats and loses contact
Safe checks before calling for service
- Check that the cabinet plug is fully seated in the outlet.
- Make sure the cabinet is on its own circuit and not sharing with a heavy load.
- Read the air and the product with a thermometer rather than trusting the display.
- If the alarm repeats, call us to schedule service.
- Ask your electrician about the supply, and write down when the alarm appears.
How a technician diagnoses error code UHi / uLo
- Read which voltage alarm is active and when it started.
- Measure the voltage at the outlet with and without other loads running.
- Inspect the plug, cord and outlet for heat marks.
- Check the voltage reading at the cabinet against the meter.
- Review the control's voltage alarm limits.
- Recommend a supply correction before replacing any part.
- Measuring supply voltage means live 115 V or higher circuits.
- A bad outlet or shared circuit is an electrician's repair, not an operator one.
- High or low voltage can damage the compressor and fan motors.
Technical reference
- Document
- Commercial Refrigeration General Control Guide TEC_TM_001 Rev C, Danfoss ERC Display Code Definitions
- Edition
- TEC_TM_001 | REV. C | EN, 09/3/2025, P#811072
- Models / control
- Danfoss ERC
- 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 uHi a cabinet failure?
Usually not. It reports the supply voltage is too high.
Why did the compressor stop?
The control may hold it off until voltage returns to a safe range.
Will it clear?
Yes once the supply is back in range, but repeats point to a circuit problem.
Need help with True error code UHi / uLo?
A technician confirms the cause on site and gives you the price in writing before any work starts.