Sounds like not all of your elements are working. I have a similar age Enviwarm system and it charges up fine and still blows hot air out in the evening. Mine has 5 elements of 2.1kW each. If any one or more of those was to fail then the amount of heat charged up would be less. It could also be the charge controller which is switching the supply off before sufficient overnight charge has been obtained.
You probably need a good electrician to check out the elements and/or charge controller. The circuit of this unit is not particularly complicated but does need a qualified electrician to meet safety standards.
Pugwash, February 2013
