641 Chair Crash Avoidance System Troubleshooting
The Crash Avoidance System prevents damage to the chair by disabling certain functions if a potential crash position is detected.
This illustration shows only the components that are monitored by the Crash Avoidance System.
•Only the wires that affect the Crash Avoidance System are shown.
•If Power Light is On, proper voltage is present at PC Board.
•If Power Light is off, refer to Page A-2 for troubleshooting.
When Are Functions Disabled?
The main PC board continuously monitors the all four position sensors, as well as the foot extension switch.
Based on the position sensor readings, and the status of the foot extension switch, circuitry on the PC Board estimates the position of the headrest and the foot extension.
If the estimated position of the headrest indicates a potential collision with the floor, the Base Down, Tilt Up, and/or Back Down function(s) are disabled.
If the estimated position of the foot extension indicates a potential collision with the floor or the chair shrouds, the Base Down, Tilt Down, and/or Foot Down function(s) are disabled.
When Are Functions Restored?
Functionality is restored when one or more of the axis are moved out of the potential crash position.
Crash Position A: Potential Headrest Collision
One or more of the following functions may be disabled: Base Down / Tilt Up / Back Down
What Is Crash Position?
The chair is considered to be in a potential crash position when:
1.The Base, Back, and Tilt position sensors indicate that the headrest mechanism is approximately 2 in. (5 cm) from the floor*.
2.The Foot Extension switch is not tripped (indicating the foot extension is not in the stowed position), and the Base, Tilt, and Foot position sensors indicate that the foot extension cannot be moved to the stowed position without contacting the floor or chair shrouds.
*This measurement is an estimate based on normal headrest position (shown). The distance from the floor will vary with the headrest position.
Crash Position B: Potential Foot Extension Collision
One or more of the following functions may be disabled: Base Down / Tilt Down / Foot Down
Problem: One or more of the following functions not working properly: Base Down, Back Down, Tilt Up/Down and/or Foot Down. Chair is not in Crash Position.
Before performing any of the checks on this page, move the foot extension to its stowed position.
1.Calibrate PC Board Refer to: Main PC Board
2.Check for Loose / Damaged Wire Connections - Base / Tilt / Back Position Sensor wires
3.Position Sensors - Base / Back / Tilt / Foot Refer to: Position Sensors
One or more malfunctioning sensor may cause this problem to occur.
