Test sequence

WARNING: This page does not describe the selected car, but rather 14 other vehicles, including the 2005 Volkswagen Jetta, 2005 Volkswagen Golf, 2004 Volkswagen Jetta, 2004 Volkswagen Golf, and 2003 Volkswagen Jetta. However, it is still accessible from the selected car via links, so may be relevant.

Disconnect glow plug connector from glow plug.
Connect voltage tester using auxiliary clips from auxiliary cable set to battery positive (B+).

Fig 1: Connecting Voltage Tester Using Auxiliary Clips From Auxiliary Cable Set To Battery Positive

Place voltage tester probe on each glow plug one after another.
Diode lights up: glow plug OK

Diode does not light up: replace glow plug.
Remove and install glow plugs with Hinged socket 3220.
Tightening torque: 15 Nm (11 ft lb).