The instructions that came with my ATC-800+ show the following connections:
1,2 Cooling circuit
3,4 Heating circuit
5,6 The sensor
7,8 Mains in
There is no 9th terminal!!
Make sure you have an ATC-800+ as maybe the older 800 model might be different
Also remember that the heating and cooling circuits are just relay contacts to switch the live power. That means you would connect the live feed to terminal 7 and link it to terminals 1,3.
Then terminal 2 would be the switched live feed to the fridge and terminal 4 to the heater.
Hope this helps
Will