b. If your problem is that the foot switch fails to raise or lower the chair, there are
three probable causes from a list of all possible causes. Refer to the appendix.
(1) The chain could be broken. You test this by visually inspecting. If
broken, you replace it.
(2) The pin on the motor sprocket could be sheared. Test by visually
inspecting. If sheared, replace the motor. Refer to Lesson 3, Remove and Replace or
Repair Defective Components of the Dental Chair and Stool.
(3) You could have a faulty foot switch or wiring harness. Test by using the
following procedures.
(a) Remove the foot switch from the pedestal.
(b) Use a voltmeter to check for a reading of 115v or 220v, as
applicable, between terminal 2 and the neutral line. If there is no reading, the wiring
harness is faulty. Replace the wiring harness.
(c) If there is a reading in (b) above, check for a reading of 115v or
220v as applicable between terminal 3 and the neutral line when you depress the left
side of the foot switch. Also check for the same reading between terminal 1 and the
neutral line when you depress the right side of the foot switch. If there is no reading, the
foot switch is faulty. Refer to Lesson 3, Remove and Replace or Repair Defective
Components of the Dental Chair and Stool.
(d) If there is a reading on both switch legs, the motor is faulty. Refer
to Lesson 3, Remove and Replace or Repair Defective Components of the Dental Chair
and Stool.
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