647 Chair Base Actuator / Limit Switches Test and Repair

This illustration shows the base limit switches and the three serviceable components of the base actuator. Use the table below to isolate the malfunction.

647 Chair Base Actuator Limit Switches

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.

Perform Limit Switch / Harness Test

647 Chair Limit Switch Harness Test

1.Disconnect harness from J13 on main PC board.

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

3.Place other probe on the wire corresponding the desired switch, see illustration.

Check switch tripped and untripped.

With Switch Untripped

Meter Reading

Required Action

OL

Limit switch / harness OK, Perform Limit Switch Continuity 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

Limit switch / harness OK, Perform

 

647 Chair Limit Switch ContinuityTest

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 base actuator wires, J1 and J2.

2.Place meter probes on actuator wires. 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, J1. Place other probe on PC board ground wire. Check meter reading.

2.Repeat for J2.

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
Equipment Alert

This test cannot be performed if either base limit switch is tripped.

647 Chair Max/Min Positions

1.Move back section so that it is approximately halfway between its maximum and minimum positions.

647 Chair Base Limit Switch Bracket

2.If necessary, remove base limit switch bracket. Switch wires must remain connected.

647 Chair PC Board Test

3.Tag, then disconnect base actuator wires from J1 and J2.

4.Move wire from J3 to J1. Move wire from J4 to J2.

Equipment Alert

The back limit switches will not stop movement during this test. Do not run past max / min positions.

5.Press and hold Base Up button for 5 seconds. Does back section move up briefly, then stop and beep? If YES, go to Step 6. If NO, replace PC board.

6.Press and hold Base Down button for 5 seconds. Does back section move down briefly, then stop and beep? If YES, PC board is OK. If NO, replace PC board.