1990 Intl 4600 truck w/ DT 444, change the glow plugs to manual

Looking to change from glow plug controller to a manual switch . I have the relay , switch , and instructions. The problem is there are three 12V battery type cables going to the hot terminal on the relay, one smaller battery type cable on the other large terminal , and only one wire going to one ( there is only one ) small terminal ) on the existing relay with a ground attached to this small terminal and the fire wall. All wires are red . Not sure if someone added cables to this relay , but it’s not the setup that the instructions show on how to disconnect the controller. The relay is mounted mid fire wall. Anyone have any ideas as to what the set up is with this