Ok you would need to unplug the unit from the wall, Go around the front, around the door aperture you will see the door switch for the fridge. Lever this out with a screw driver, disconnect the wires, put your testers on the switch after the wires are moved, the switch should read open when pushed (needle does not move) then when the switch is released the needle will move. If in both positions the needle does not move replace the door switch, if the needle does move replace the light assembly.
Another way to test this is to remove the light assembly, disconnect it from the wire harness, set your meter to the dc volts range and with the door open you should read 12v dc, if you have 12 v dc then the light assembly is bad.Click here to order the light assembly
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