how to program my new fob to a ford mondeo lx zetec 97 ?

I posted a question late last year and the answer was very helpful. But i have bought a new fob key for my mondeo, I know the key works the light does flash I was given instructions on how to program it but part of the instruction was turn the key to the I possition and the PATS LED will light up then turn the key to 0, but my PATS LED is flashing all the time, it only goes off when the engine is on or the key is in the II possition. I still continued with the programming but to now pervale. Could the problem be with the car system? please help:-)