Audi A3 Clocks

firstly its a first for me so a big hello to all, and to say how i think the response to other member queries are a credit to you all.

now down to the biz, remember be gentle with me as it is my first time.
i have tried to change the instrument clocks in my 1999 a3 but when fitted and all plugged up the immobiliser light flashes and of course the engine will not fire up.
any thoughts on this would be grateful,