How an HIU actuator fails
Thermal actuators fail open or closed and give no warning. Motorised actuators more often fail slowly — the gear train wears, the stroke shortens and the valve no longer reaches full travel, so the unit half-works. Electrical faults in the supply or control signal produce the same symptoms as a dead actuator, so we test the drive signal at the actuator terminals before condemning the part. That five-minute check regularly saves the cost of an unnecessary component.
- Actuator dead with a healthy control signal
- Reduced stroke and partial valve travel
- Noisy or continuously running motorised heads
- Thermal head stuck in the open or closed position
- Wiring, connector and supply voltage faults
