Electrical question cooling fan

[daberry]

My fan is being ran manually using a dash switch. Someone has wired it through a relay mounted to the dash. I also see this scotch lock 143389 above the fan relay in the RF fuse panel.

I'm wanting to rewire it to run on engine temperature.

Thanks, Dale

[CraigS]

I have no idea on the scotchlock but do you know what the dash switch does? It either provides ground or power to the relay. If it is ground then all you need to do it tee into that wire and run it to a temp sender usually in the intake manifold. That way the fan is controlled both automatically and/or by you. I like this because I can hit the fan switch when I see I will be in traffic and that way the temp stays pretty steady. I like that better than it going to 195, fan on, fan off at 180, back up to 195.

[daberry]

I figured out the relay at the fan switch. It just didn't follow the normal relay setup. Not an electrician so took a few minutes before I was confident in what they had done. I'm going to rewire it more conventionally.

Curious why they wouldn't just use the RF relay, figure that scotch lock has something to do with it.

[Papa]

To amplify what Craig said, install a thermostatic switch in the radiator or the intake manifold and that typically will complete a ground connection at the temperature that the switch operates at. It's more common to control a fan relay by completing the ground than by applying power because of the way the temp switches work.

Dave