Hi I drive a 2006 Vw Transporter 2.8 TDI, the glow plug light

Could be brake light switch

most likely the brake light switch

Give some more details of the problem.

Classic 109 relay failure.

Relay is for the Glow Plug system.

This relay provides the power to all of a TDI's engine-based electronics.

If the glow plug light comes on intermittently by itself, check your brake lights too.

A burned-out bulb will cause the glow plug indicator light to come on. Sometimes flashing is caused by a bad Brake Lamp Switch on the Brake Pedal. It was updated for free by VW .

If you can see it under the knee panel, the Brake Lamp Switch body should be Metallic Green....if it is Purple or Black it need updated.

The glow plug light in VW cars are telling you you have a fault not with the glow plugs but with the engine management.Get a garage to do a diagnostic check for you.

Try this website for resolving car problems by downloading a FREE service manual for your vehicle. This is not an owners manual but a factory mechcanic's manual.

http://ezinearticles.com/?Find-the-Free-Auto-Repair-Manual-You-Need-Online&id=92717

your glow plug relay is going out you need to replace it.

i dont think it will hurt it, you might just be dealing with a loose wire

There are a number of different causes of this problem. Check all glow plugs. Check glow plug relay. If both are ok....This may seem unusual...Check the brake light switch situated at brake pedal. A faulty brake light switch will cause the glow plug light to flash
Good luck with it
John

may be time for new glow plugs.