I'm trying to wire a manual fan switch for the secondary fan because the fan switch on the passenger side is broke. So I found the relay and grounded out the green/white wire but nothing happens. Both fans kick on with the AC so I know they both work. My question does the original fan switch have to be hooked up to run a manual switch?

Also, with the AC on, I unplug the relay for the primary fan and it turns off, but when I unplug the other relay the secondary fan keeps running. Is this possibly or am I working with the wrong relay? thanks

 

Each relay if you have the correct one will shut off it's respective fan. No, the fan switch can be unplugged and a manual switch will trigger the aux fan. Remember grounding the aux fan wire will turn on BOTH fans. The ECM defaults if the aux is turned on before the primary does. Key must be on even for the manual switch. Make sure you have a good ground for the manual. The fan switch in the block works like this, when the temp reaches 243 degrees it grounds the single wire going to it internally through the mounting threads and energizes the fan relay. Putting a ground to the correct wire does exactly the same thing.