TDI 170 glow plug light not illuminating and car won't start

Hi,

Has anyone heard of an issue where the glow plug light doesn't come on when you switch ignition on? Mine is doing that and in this cold weather it obviously won't start.

I don't understand why they aren't coming on though? If I put the ignition on about 5 time the glow plug light does eventually switch on and it starts

Coolant temp is working fine when it's driving. Mk2 2.0 tdi 170

Many thanks