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

Problem	Required Action
Motor runs, but makes grinding noise.	Clean / lube actuator threads. Replace actuator if necessary.
Motor runs, but table does not move.	Inspect / replace motor coupler.
Motor does not run.	Check limit switch wire connections. If OK Perform Actuator Motor Test.

Lube threads w/lithium grease.

1.Disconnect harness from J11 on main PC board

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

3.Place other meter probe on the wire corresponding to the desired switch - see illustration.

Back Down switch untripped OR Back Up Switch tripped

Meter Reading	Required Action
OL	Perform Limit Switch Harness Test
less than 10 Ω	Limit switch / harness - OK, Perform Actuator Motor Test

Back Down switch tripped OR Back Up Switch untripped

Meter Reading	Required Action
less than 10 Ω	Perform Limit Switch Harness Test
OL	Limit switch / harness - OK, Perform Actuator Motor Test

1.Unplug the appropriate limit switch harness.

2.Measure continuity.

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

1.Tag / disconnect back actuator wires J3 and J4.

2.Place meter probes on actuator wires. Check meter reading.

Meter Reading	Status	Required Action
1 to 10 Ω		Actuator motor OK. Perform Motor Ground Test
OL or less than 1 Ω		Replace motor.

1.Place one meter probe on actuator wire J3. Place other meter probe on PC board ground wire. Check meter reading. Repeat for J4.

Meter Reading	Status	Required Action
OL or more than 1 M Ω		Motor harness OK. Perform PC Board Test
less than 1 Ω		Replace motor.

1.This test cannot be performed with the back section in the max. or min. position. If necessary, reposition the back section. Refer to: Base Actuator - PC Board Test.

2.Move the Base function so that it is approximately halfway between the maximum and minimum positions.

3.Tag, then disconnect back actuator wires from J3 and J4.

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

5.Press and hold Back Up button for 5 seconds. Does the base move up, then stop and beep? If Yes, go to Step 6. If No, replace PC Board*.

6.Press and hold Back Down button for 5 seconds. Does the base move down, then stop and beep? If Yes, PC Board is OK. If No, replace PC Board*.