how can i change the internal bulb ?

It's a fiddly job & not simple. I had a similar problem with my M reg Cavalier GLS. You have to remove nearly all the facia panels from the steering wheel side to get to the bits behind the heater control panel. Do not remove the steering wheel. Go to your nearest library and get the Haynes Manual for your car model and follow that. It's what I did. Good luck. There is also a lot of help on the VX owners club website. Google the site & try there.

Ross Godlieb
September 2009