This bulletin applies to all Volkswagen vehicles equipped with a TDI diesel engine. Under certain conditions, you may hear the glow plug relay J52 clicking on and off after the engine is started.
Once the engine has been started, the after-glow period could last up to three minutes or until the engine coolant reaches 140 degrees Fahrenheit and engine rpms are below 2,500.
Under these conditions you may hear the relay clicking on and off while shifting. This is because the rpms are going above and below 2,500. The relay location is in the plenum near the wiper motor.