Glow Plug indicator light problem

[cameron1307]

Our glow plug indicator light keeps flickering on and off while driving along. It also sometimes stays lite for a long time before starting but not necesserily when the engine is first started or when the weather is cold. Is this suggesting a problem?

Multivan 1989 1.6TD.

[Mocki]

i would look at the black box in the engine bay where the glow plug relay lives, and be checking for wire damage, bad connections and poor earths in the system.....