continuous heating?

I have been called to a turbomax 242
That has permanent heating.
There are no external controls, just an integral programmer.

The heating control stat is set to its lowest point.
I have disconnected programmer from the board.
Terminals 3+4 are linked. So that its running on stats only. Still runs continuously. Suspect its the board
has any one else come across continuous heating on a turbomax.

Tony
June 2009