Where does this temp sensor go?

[Ozmobs]

I have a ducted reverse cycle system, a water-cooled package.

It's coming up with "fault" on the panel when heating after a few minutes and the compressor shuts down for about 5 minutes before it tries again.

I've narrowed the problem down to the coil temperature sensor - when unplugged, there is no "fault" message or shutdown, however that sensor needs to be there and plugged in.

The only problem is, I'm not sure where it's supposed to go.

IMG_20130612_201114.jpg

I've attached a picture of the coil temperature sensor. I've circled two places, a green circle and a red circle. The line at the green circle goes to the heat exchange for heating/cooling the apartment, and the red circle is the water line that goes back up to the roof.

Where do you think it should go?