how do i refit the stopper and spring behing the water tank on ZanussTC7114?

The warning light has been coming on on my Zanussi TC7114 condenser dryer when the water tank is not full. I have taken out the tank ,and the stopper and spring have fallen out at the back of the tank. I have replaced them both several different ways but the light continues to come back on and the machine stop working after several minutes. I am assuming I have put them back in
the wrong way but can't find any advice in the instruction book. Can anybody help!