inspect rheostat operation
Connect the positive (+) lead from the battery to terminal
1. Connect the negative (-) lead to terminal 4.
(a) With the brightness at minimum, check that there is 9V between terminals 1 and 3.
(b) Gradually turn the rheostat toward the brighter side and check that the voltage between terminals 1 and 3 decreases from 9V to OV.
(c) With the brightness at minimum, check that there is OV between terminals 2 and 4 and 12V when brightness is at any other level.
If operation is not as specified, replace the rheostat.
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