647 Chair Tilt Actuator / Limit Switch Test and Repair

This illustration shows the tilt down limit switch and the three serviceable components of the tilt actuator. Use the table below to isolate the malfunction.

647 Chair Actuator Limit Switch

Problem

Required Action

Motor runs, but makes grinding noise.

Clean / lube actuator threads. Replace actuator if necessary

Motor runs, but chair does not move.

Inspect / replace motor coupler.
Motor does not run.

Up only - Perform Output Voltage Test at Tilt Sensor

Down only - Perform limit Switch Test.

Up and Down - Perform Actuator Motor Test.

647 Chair Tilt Actuator Limit Switch and Harness Test

1.Disconnect harness from J11 on main PC board.

2.Place one meter probe on the common, white.

3.Place other probe on the Tilt Down limit switch, red.

Check switch tripped and untripped.

With Switch Untripped

Meter Reading

Required Action

OL

Perform Limit Switch Harness Test
Less than 10 ohms

Limit Switch / Harness OK, Perform Actuator Motor Test
With Switch Tripped

Meter Reading

Required Action

OL

Limit Switch / Harness OK Perform Actuator Motor Test
Less than 10 ohms

Perform Limit Switch Harness Test

647 Chair Limit Switch Harness Test

1.Unplug the appropriate limit switch harness.

2.Measure continuity.

When

Meter reading should be
Actuator Full Up

White to Black - Open

White to Red - Closed

Actuator Full Down

White to Black - Closed

White to Red - Open
Actuator Midway Point

White to Black - Closed

White to Red - Closed

647 Chair Limit Switch Continuity Test

1.Disconnect wires from switch.

2.Place meter probes on COM and NC terminals.

Check switch tripped and untripped.

With Switch Untripped

Meter Reading

Required Action

OL

Replace Limit Switch

Less than 5 ohms

Limit Switch OK. Replace Limit Switch Harness
With Switch Tripped

Meter Reading

Required Action

OL

Limit Switch OK. Replace Limit Switch Harness

Less than 5 ohms

Replace Limit Switch

647 Chair Actuator Motor Test

1.Tag and disconnect tilt actuator wires, J7 and J8.

2.Place meter probes on actuator wires.

3.Check meter reading.

Meter Reading

Required Action

1 to 10 ohms

Actuator motor OK. Perform Motor Ground Test

OL or less than 1 ohm

Replace actuator motor

647 Chair Motor Ground Test

1.Place one meter probe on actuator wire J7. Place other probe on PC board ground wire.

2.Check meter reading.

3.Repeat for J8.

Meter Reading

Required Action

OL or more than 1 mega-ohm

Motor Harness OK. Perform PC Board Test

Less than 1 ohm

Replace actuator motor

647 Chair PC Board Test

1.Tag, then disconnect tilt actuator wires from J7 and J8.

2.Place meter probes on J7 and J8 terminals on PC board. Set Meter to VDC setting.

3.Activate the Tilt Up function. Check meter reading.

4.Repeat for Tilt Down function.

Meter Reading

Required Action

Approx 48 VDC

PC board OK

Out of range

Replace PC board