How can I check if my auxiliary wiring/relay is working?
As I understand fan switch supposed to turn on the auxiliary fan when water temperature hits 100 degrees C. Since the fan switch got a single wire I assume that it just makes a ground connection once the switch heats up. So I tried to just ground the wire directly to see if the fan turns on or not, but nothing happened. Is there some other condition that has to be met for the auxiliary fan to turn on or is that a sign that there is something wrong with my auxiliary fan relay or wiring?

P.S. Where is the auxiliary fan relay located?