Filament Check

When measuring voltage, wrap tin foil around the top of the negative probe. Then press the foil against the wire with your finger.

Fig 1: Wrapping Tin Foil Around The Top Of The Negative Probe, Then Pressing Foil Against Wire
Courtesy of NISSAN MOTOR CO., U.S.A.
Attach probe circuit tester (in Volt range) to middle portion of each filament.

Fig 2: Attaching Probe Circuit Tester (In Volt Range) To Middle Portion Of Each Filament
Courtesy of NISSAN MOTOR CO., U.S.A.
If a filament is burned out, circuit tester registers 0 or battery voltage.
To locate burned out point, move probe to left and right along filament. Test needle will swing abruptly when probe passes the point.

Fig 3: Moving Probe To Left And Right Along Filament To Locate Burned Out Point
Courtesy of NISSAN MOTOR CO., U.S.A.