Passat 1.9 tdi b5.5 glow plug light

[marshy1987]

Hi all needing some help recently bought a passat last week the other day the glow plug light started flashing then engine workshop i have done some looking about people are saying brake light switch but my brake lights are all working fine but after driving awhile the glow plug light goes of and dont come back on went out today started driving it came on again cars boosting fine and it still pulls through rev range could it be a case of a faulty switch anyways even though brake lights are working or could it be something else any help appreciate it thanks☺