Why are the relays clicking on my IT summing card?

 I am using a HI215IT-PS1 summing box, 3 Hardy load cells and a Hardy weight controller or PLC module. We are also using C2 cable between summing box and Hardy Instrument, and we are hearing a very loud clicking noise at the summing box. What can be causing this?

This response would apply to all Hardy weight controllers or PLC Modules as they will all work with the HI 215IT summing PCB. 

The HI 215IT summing board or box includes relays on the printed circuit board. These relays can make noise or "chatter" if the C2 wires are installed incorrectly. Also, the sense jumpers should be removed and sense lines installed. The clicking indicates there is not a return path for the IT relays.  That return path is through the C2 wires. You should also make sure the plug connectors on the summing card are plugged in correctly.  If one is installed incorrectly, it can cause a fault in the card.