Hotpoint CTD80G problems?

I have a Hotpoint CTD80G Condensing Dryer. On the screen the empty water flashes even when the water reservoir is empty? I have changed the pump and also the heat element with thermostats? There are no error codes flashing up? It stays on for about 3 minutes and then stops? I am now at the end of my very long teather and i certainly dont want to pay for a engineer to come out as i can do it myself if i am directed to the problem? Please HELP!!