Jumper or switch to run radiator fan in addition to H/E with fans?

[ZOMBEAST]

Just curious if any one has done this, or if it would even make sense.

My thought is to run rad fan on high regardless of temp to assist my dual fan H/E for drag racing.

I currently have the stock rad fan/assy, but I've got the upgraded version coming.

 

[Willie]

Let me look...... ummmm... I think I have... I have so much junk that I forget....>>

 

[ZOMBEAST]

LOL! Why am I not surprised that you've done this?

Can you switch power to the high fan speed wire regardless of the low speed operation? Or do you have to isolate the low speed when manually powering the high speed? I'm not sure if this is something the PCM would do, or if they can be powered at the same time.

 

[Willie]

LOL! Why am I not surprised that you've done this?

What can I say, man? I'm turning out to be the one-stop shopping dude, huh?

Can you switch power to the high fan speed wire regardless of the low speed operation? Or do you have to isolate the low speed when manually powering the high speed? I'm not sure if this is something the PCM would do, or if they can be powered at the same time.

When I first tackled Ford's low / high speed fan design, a first for me as my old Camaros did not have this design, but had two fans. Anyways, notice in my pic of my upper console that I have a low-speed fan LED, but no way to manually turn it on, like I do the high-speed. I went on to design the circuit so that regardless of whether the PCM has the low-speed commanded or not, my high-speed works. If low-speed is on and I flip the switch, low-speed turns off, replaced by the high-speed. So the answer to your question is YES, you can switch to high-speed regardless. Basically, you're messing the PCM operation without the PCM knowing your screwing with it...

The added circuitry includes an SPDT relay and a couple of 1N4005 diodes, and a switch of course. That's it.

 

[ZOMBEAST]

So you are using a switch activated SPDT relay to power the high speed and lock out the low speed? Interesting is the addition of the diodes. Do you have these pre-relay as insurance to prevent back feeding voltage? Very curious as to where and why you're using them. Might need a diagram.

Edit: I made up a diagram minus the diodes with an SPDT. Can't figure it out. Maybe with a DPDT.

 

[Willie]

I think at this time, the schematic will speak one thousand words. Agreed?