| Power Fault | External 24V power supply is short circuit or the load of External 24V power supply is too large |
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ERR36 – External 24V Power Fault
What this means
ERR36 indicates a problem with the external 24V power supply circuit used by the VFD for control logic, I/O, or external devices.
In simple terms:
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The VFD’s 24V output or input is overloaded or shorted
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The VFD detects unsafe current draw on that circuit
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The VFD shuts down to protect its internal power supply
This error is not related to spindle load, cutting conditions, or RPM.
What the 24V Circuit Is Used For
The external 24V supply is commonly used for:
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Control inputs and outputs
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Sensors, proximity switches
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Relays, solenoids
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ATC-related control logic
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External fault or safety circuits
It is not designed to power high-current devices.
Most Common Causes
1. Short circuit on the 24V line
The most common cause.
Examples:
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Pinched or damaged control wiring
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Miswired connector
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Stray wire strands contacting ground or another terminal
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Incorrect pinout on aviation connectors
2. Too much load on the 24V supply
The VFD’s internal 24V supply has limited current capacity.
Common mistakes:
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Powering solenoids directly from the VFD
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Driving multiple relays without external power
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Powering lights, fans, or accessories from the VFD
The VFD will fault if the current draw exceeds its limit.
3. Incorrect wiring during modifications
ERR36 often appears after:
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Adding accessories
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Rewiring control cables
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Installing custom ATC components
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Modifying safety circuits
4. Failed external device
A connected device may have:
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Internally shorted
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Failed coil
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Wiring damage
This can overload the VFD’s 24V output even if wiring appears correct.
What to Check First
Step 1: Power down completely
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Turn off the VFD
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Disconnect input power
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Wait 2–3 minutes
Step 2: Disconnect all 24V accessories
Temporarily disconnect:
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External sensors
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Relays
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Solenoids
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ATC components
Then power the VFD back on.
If ERR36 clears, reconnect devices one at a time to identify the culprit.
Step 3: Inspect wiring carefully
Look for:
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Crushed insulation
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Exposed conductors
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Loose terminal screws
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Incorrect pin assignments
Step 4: Verify current draw
If powering external devices:
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Confirm their current requirements
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Use an external 24V power supply for higher loads
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Use the VFD’s 24V only for signal-level devices
What Will Not Fix ERR36
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Changing feeds or speeds
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Adjusting acceleration
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Re-running motor identification
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Power cycling without fixing wiring
ERR36 will return until the electrical issue is corrected.
Best Practices to Prevent ERR36
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Use the VFD’s 24V only for low-current signals
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Power solenoids and actuators from an external supply
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Add fuses to accessory circuits
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Double-check pinouts before powering on
Summary
ERR36 means the VFD’s external 24V circuit is overloaded or shorted.
Most common causes:
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Wiring short
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Too many devices on 24V
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Failed external component
This is a wiring and accessory integration issue, not a spindle or VFD tuning problem.
