Place ferrite cores on encoder cables and install line reactors on the AC input to reduce electrical noise.
If you have exhausted all the steps above and H66 persists, professional intervention is needed. Contact Yaskawa support with the following ready: yaskawa error code h66
The H66 fault occurs when the braking resistor temperature exceeds its allowable limit. This mechanism is designed to protect the hardware—specifically Yaskawa’s 3% duty cycle resistors—from thermal damage. Yaskawa America Common Causes High Duty Cycle Place ferrite cores on encoder cables and install
Check the ribbon cable from the control board to the gate drive board for any signs of damage or loose pins. 2. Verify Parameter Settings yaskawa error code h66