T100 SR5 Extra Cab Pickup 4WD V6-3.4L (5VZ-FE) (1998)
Dimmer Switch: Testing and Inspection
INSPECT LIGHT CONTROL RHEOSTAT
a. Connect terminals 1 and 3 through a 3.4 W test bulb.
b. Connect the positive (+) lead from the battery to terminal 1 and the negative (-) lead to terminal 2.
c. Turn the rheostat knob fully counterclockwise, check that the test bulb goes out.
d. Gradually turn the rheostat knob clockwise, check that the test bulb brightness changes from dark to bright.
If operation is not as specified, replace the rheostat.