Any help with honda sat nav (Accord tourer) 2003?

I am having problems with my honda sat nav system. When I boot the system it starts up and you can do the usual stuff like setting target destination etc. When I turn the ignition fully on to start the engine the screen goes blank! Nothing then happens and I just have a blank screen. Sometimes the screen does come back but it is very hit and miss. Any help appricated. p.s. honda want to charge £160 plus VAT to start looking at it.