Troubleshooting Common Fault Codes for Bosch Rexroth 2AD Motors

Fault Code

Fault Name & Meaning

Typical Causes

Basic Troubleshooting Steps

F218

Drive Overtemperature (Heatsink too hot)

– Inadequate cooling or ventilation (cabinet ambient >45 °C).

– Heat sink or air vents clogged with dust; fan failure.

Improve cooling: Verify all cooling fans work and vents are clear of dust. Lower the cabinet temperature below spec. If the fault persists after cooling, the drive’s internal temperature sensor or blower might be faulty – consider drive repair.

F219

Motor Overtemperature (Motor too hot)

– Motor overloaded .

– Cooling failure on motor.

– Faulty motor temperature sensor or wiring.

Reduce load & cool: Let the motor cool and reduce the mechanical load or duty cycle if it’s running beyond its rating. Check any attached fan/blower is running and clean the motor’s cooling fins. Inspect the motor’s temperature sensor cable for damage or disconnection. Once temperatures normalize, reset the fault.

F220

Regeneration Overload (Brake resistor overload)

– Excessive regenerative energy from decelerating a large load (internal bleed resistor can’t dissipate it).

– Very high deceleration or downward motion generating too much energy back into drive.

Manage regen energy: Reduce deceleration rates in the motion program or use gentler stops so the drive isn’t overwhelmed. Check the mechanism to avoid dumping excessive energy. If high regen is unavoidable, consider installing a larger or external braking resistor to increase capacity. After adjustments, reset the fault and resume operation.

F226

Undervoltage in DC Bus (Supply voltage low)

– AC mains supply was interrupted or dipped while the drive was enabled (e.g. someone hit the main disconnect without disabling drives first).

– Incoming power sag or brownout; tripped breaker feeding the drive.

– Loose DC-bus link connections in multi-axis systems causing momentary power loss.

Stabilize power: Verify the facility power is stable and that proper shutdown procedure is followed. Inspect the mains supply for voltage drops; if frequent, use a power conditioner or UPS. In multi-axis setups, check that all DC link cables between drives and the supply module are securely connected. Once power issues are resolved, clear F226 by resetting the drive.

F228

Excessive Deviation (Following error too large)

– Commanded motion or speed change is too aggressive, exceeding the drive/motor’s capability.

– Mechanical jam or blockage in the machine preventing movement.

– Incorrect tuning or parameter set: e.g. position loop gain too high or allowable following error window too tight.

Adjust motion or clear jam: First, reduce the feed rate or acceleration in the CNC/PLC program to within safe limits of the motor/drive. Check for mechanical issues – ensure the axis can move freely and nothing is jammed or binding. Also review and retune the servo parameters: ensure the position loop gain and following error monitoring window are properly set. After fixing the cause, reset F228 and test the movement slowly to confirm the fault is gone.

F229

Encoder 1 Failure (“Quadrant error” feedback fault)

– Defective or loose encoder cable on the motor, causing loss of feedback signals.

– Electrical noise interference on the encoder lines.

– Faulty encoder hardware or a bad encoder interface in the drive controller.

Check feedback system: Inspect the motor’s encoder cable and connections; replace the cable if any damage or intermittent connection is found. Ensure the feedback cable is properly shielded and routed away from high-voltage motor cables to prevent EMI noise. If the error persists, the encoder itself might be bad or the drive’s encoder-reader circuitry is faulty. Persistent F229 faults likely require professional repair of the encoder or drive.

F248

Low Battery Voltage (Encoder backup battery low)

– The backup battery for the motor’s absolute encoder is nearly depleted.

– If a new battery was installed, F248 could indicate it wasn’t connected properly or is the wrong type.

Replace battery: Plan to replace the encoder backup battery as soon as possible. The drive triggers F248 when the battery voltage drops below ~2.8 V to give you a grace period for replacement. Locate the battery and install a fresh, correct battery. After putting in a new battery, reset the fault.

F860

Overcurrent Fault (Short or excess current draw)

– Short circuit in the motor’s power phases or cabling.

– Drive parameters misconfigured, causing unstable current spikes.

– Internal hardware failure in the drive’s power output stage.

Inspect power circuit: Check the motor’s power cable for damage or pinched wires. Use a multimeter or megohmmeter to test the motor windings for shorts between phases or to ground. Fix any wiring problems or replace the motor if the windings are faulty. Verify the drive’s current limit settings and restore them to default if they were set improperly – bad tuning can cause oscillations and overcurrent trips. If F860 still recurs with everything else ruled out, the drive’s output transistors might be defective. In that case, the drive needs professional repair.

F234/ F434

Emergency Stop Activated (Safety circuit triggered)

– An emergency stop (E-stop) button was pressed by an operator, or a safety interlock opened.

– A fault in the E-stop wiring or a malfunctioning safety relay caused a false trigger when no actual emergency exists.

Reset safety & drive: First, check why the E-stop was triggered – ensure no real emergency or hazard is present on the machine. If an E-stop button was hit, reset and release it. If a safety gate or relay tripped, inspect those circuits and reset them once it’s safe. After all safety circuits are closed again, you can clear the F234/F434 fault by pressing the drive’s reset button and re-enable the drive. If the E-stop fault won’t clear, examine the wiring and safety devices for defects or loose connections that might be falsely cutting the circuit.

F277

Internal Hardware Fault (Drive self-diagnosis error)

– The drive’s self-diagnostics detected an internal hardware problem.

– Sometimes occurs after a failed firmware update or if an internal calibration value is corrupt.

Power cycle & repair: There is no user fix for an F277 error beyond trying a full power reset of the drive to see if it was a one-time glitch. If the fault reappears consistently, it indicates the drive electronics are compromised. Do not repeatedly reset and run.