Hobart Legacy+ Mixer Error LU: Under Voltage
LU is the under voltage code on Hobart Legacy+ HL800 and HL1400 mixers, and the motor drive stops the motor when supply voltage drops too low. Stop the mixer, keep the guard closed, and check that the plug or disconnect is firmly on and the breaker has not tripped. Cycle power once and try a lighter batch; if LU returns, stop and call us.
High: low voltage stops the mixer, and a poor connection behind it can overheat if left alone.
What does Hobart error code LU mean?
A motor drive needs a minimum supply voltage to run the motor safely. When the voltage sags below that, when power is interrupted for a moment, or when the drive itself is not working right, the drive stops the motor and shows LU on the SmartTimer display. The code holds until power is cycled and the cause is fixed, and the mixer will not run while it shows. Starting the mixer under a heavy load asks for the most current, so that is when a weak supply drops lowest. Low voltage can come from the building, a long cable or a loose connection, and the display cannot tell which. A heavily loaded kitchen circuit on a hot afternoon is a common place to see it. A mixer that keeps starting on low voltage works the drive hard, so repeats should not be ignored. The manual lists supply voltage at the mixer while the motor starts, loose or burned connections at the disconnect and drive input, other equipment on the same circuit, and the drive, once supply is ruled out. The text is LU.
Affected models and control systems
Hobart Legacy+ HL800 and HL1400 mixers with the motor drive and SmartTimer display. Other generations of Hobart mixers may name this differently.
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
- LU on the SmartTimer display
- Mixer stops when the motor starts under load
- Lights or other equipment dipping at the same moment
Possible causes
Listed in Hobart's documentation
- Supply voltage at the mixer while the motor starts under load
- Loose or burned connections at the disconnect and drive input
- Other equipment sharing the circuit
- Drive, once supply is ruled out
Other likely causes — what usually sits behind error code LU on this control. A technician confirms which one it is before any part is replaced.
- A hot plug or receptacle whose contacts have burned and now add resistance under load
- A heavy dough batch that pulls more current than the weak feeder can deliver
Safe checks before calling for service
- Stop the mixer and keep the bowl guard closed.
- Check that the mixer is plugged in firmly or its disconnect is fully on, and that the breaker has not tripped.
- Cycle power to the mixer once and try a lighter batch.
- If LU returns, stop and call us.
- Tell us what was running nearby and whether the plug felt warm.
How a technician diagnoses error code LU
- Read LU and record load and what else is on the circuit.
- Measure supply voltage at the mixer idle and while the motor starts.
- Inspect the plug, receptacle and disconnect for heat marks.
- Check feeder wire size, length and lug tightness.
- Compare drive input readings with supply readings to find the drop.
- Replace the drive only after a stable supply is proven and LU still occurs.
- Measuring voltage while the mixer starts is live 208 to 240 V work.
- Burned plug or disconnect contacts can lead to a fire if the mixer keeps starting on them.
- We measure voltage at the machine while it starts, then check the connections before touching the drive.
Technical reference
- Document
- Large Capacity Mixers Customer Maintenance Manual F48065 (10-22), Diagnostic Error Codes
- Maker documentation
- Hobart owner support
- Edition
- F48065
- Models / control
- Legacy+ HL800 / HL1400 motor drive + SmartTimer display
- Section
- Diagnostic Error Codes HL800 & HL1400, PDF pp. 9-11
- 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 Hobart mixer error codes
Does LU mean the drive is bad?
Not usually. The supply is more often the cause.
Why only on heavy batches?
Starting under load draws the most current, so a weak supply shows up then.
Is a warm plug normal?
No. A warm plug points to a poor connection that needs attention.
Need help with Hobart error code LU?
A technician confirms the cause on site and gives you the price in writing before any work starts.