I think you can find that info on vintage air web site and they have a YouTube video as well how to hook up a fan with trinity switch if you talking radiator cooling fan

 

Try this site: Relay Wiring Diagrams | the12volt.com

You'll probably find a relay wiring diagram that will answer your question.

 

Try this site: Relay Wiring Diagrams | the12volt.com

You'll probably find a relay wiring diagram that will answer your question.

That's a great resource! Like everything you ever wanted to wire with a relay!

 

Do you have a single 2 speed fan or 2 separate fans? The 3 relay system is for 2 fans to run both at half speed or both at full speed. Some single 2 speed fans may not work with the 3 relay system.
What is controlling the relays? You need 2 temp switches or a electronic controller or ECM with the 3 relay system to work.
Here's the 3 relay diagram for 2 fans: Relay 4 is an over ride.

 

I was looking to buy a 2 speed 17" fan. However, I think I will just buy a single speed 17". There are plenty of wiring diagrams for single speed and a lot less confusion. Then all I need to do is cut the 2 wires ground and trinary, splice them onto the current fan wires.
Thanks to all members that had replied with their thoughts/ideas/drawings.
I appreciate it.