ABB ACS580 Warning A5EA Measurement Circuit Temperature

Getting the A5EA warning on your ABB ACS580? Learn why this internal temperature sensor fault occurs and follow our step-by-step hardware troubleshooting guide.

 

In the world of Variable Frequency Drives, temperature is everything. To protect its sensitive internal components, the ABB ACS580 uses several built-in sensors. However, when you see Warning A5EA: Measurement circuit temperature, the drive is telling you something very specific: it has lost its ability to measure its own heat.

This is not a standard "overtemperature" alarm (where the drive is simply too hot). Instead, A5EA indicates a circuit failure. If the drive cannot see the temperature, it cannot protect itself, which is why this warning is a critical precursor to a hardware lockout. Here is a human-made guide to help you diagnose and resolve this internal fault.

What Exactly is the A5EA Warning?

The ACS580 monitors the temperature of its IGBTs (Insulated Gate Bipolar Transistors) and its internal control unit using thermistors. The A5EA warning triggers when the control board receives a signal that is electrically "impossible" (e.g., a voltage that translates to -50°C or +200°C). Essentially, the drive's internal thermometer is broken or disconnected.

Common Causes of A5EA

Since this is a measurement circuit issue, the problem is almost always physical and internal to the drive:

• Loose Internal Ribbon Cables: The connection between the power module (where the heat is) and the control unit (where the brain is) has wiggled loose.
• Failed Thermistor: The actual temperature-sensing component on the power module has failed (opened or shorted).
• Control Board Hardware Glitch: The Analog-to-Digital (A/D) converter on the main board is malfunctioning.
• Moisture or Corrosion: Conductive dust or humidity has bridged the pins on the measurement circuit.

Safety Warning: VFDs contain high-voltage capacitors. Before opening the drive, disconnect the main power and wait at least 5 to 10 minutes for the DC bus to discharge. Always verify zero voltage with a multimeter before touching internal components.

Step-by-Step Troubleshooting Guide

1. The "Cold Boot" Reset

Sometimes, the internal logic that processes sensor data gets stuck. A simple power toggle isn't enough; you need a full discharge.

• Turn off the main AC supply.
• If the drive uses an external 24V DC supply for the control unit, ensure that is also turned off.
• Wait 10 minutes until the screen and all LEDs are completely dark.
• Restore power. If the warning was a transient logic glitch, it should clear.

2. Inspect Internal Cable Connections

Vibration is a common cause of A5EA in industrial environments. If the ribbon cable connecting the power unit to the control unit is loose, the temperature signal will drop out.

• Open the drive cover (after ensuring it is de-energized).
• Locate the ribbon cables or the multi-pin plug that bridges the two main boards.
• Unplug and re-seat these cables firmly. Check for any signs of "soot" or corrosion on the pins.

3. Check for Environmental Damage

If the drive is mounted in a harsh environment, inspect the boards for:

• Condensation: If the drive is in a humid area, moisture can short out the low-voltage sensor lines.
• Metallic Dust: Conductive dust from grinding or machining can settle on the board, causing "ghost" sensor readings. Clean with dry, low-pressure compressed air if necessary.

4. Hardware Diagnostic (The "Last Resort")

If you have re-seated the cables and power-cycled the unit but the A5EA warning remains, you are likely looking at a hardware failure.

• Control Unit (CCU): The board may need replacement if the sensing circuit is fried.
• Power Module: If the thermistor embedded in the IGBT module is dead, the entire power section may require service.

Summary Checklist

Checkpoint	Action	Desired Outcome
Power Cycle	Full 10-minute discharge.	Clears temporary logic errors.
Ribbon Cables	Unplug and re-seat internal plugs.	Restores signal from sensor to brain.
Cleanliness	Blow out dust with compressed air.	Removes conductive paths between pins.
Replacement	Contact ABB Support for board swap.	Fixes permanent hardware damage.

Conclusion

The A5EA warning on an ABB ACS580 is the drive's way of saying "I'm blind to my own temperature." Start with a deep power cycle and a check of the internal ribbon cables. If these steps don't work, it is a clear sign that a physical board component has failed. Because measurement circuits are not typically field-repairable, the control unit or power module will likely need to be replaced.