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Discussion Starter #1
I'm using a FAST 2.0 EZ EFI system on my car. The computer wants to control(adjustable via keypad) the fan. I have the sensor installed into the manifold by the water neck and that sensor plug goes back into the main EFI harness. I have a blue wire labeled "Fan1 Relay" with a 1 amp inline fuse coming out of the main harness of the EFI. I would also like to run a manual toggle on the dash as well. I'm using the Ron Francis wiring for the car / dash.
Here is a picture of how they want the fan and switch wired...help please! The only thing they provided in the picture is the "Fan Relay" wire (long blue wire). This is the last wiring obstacle I have!

Thanks, Ryan
 

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FFCobra Captain
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Relays were really confusing to me when I built my first car. Think of it as an automatic light switch...when the switch is flipped, power runs through to the fan.

Post 86 - the relay needs power to work, so run a wire from somewhere in your harness that only gets power when the key is turned on. If you have a radio wire (and you're not using a radio) coming out of the fuse box, that's an easy choice. Note...make sure you don't have power hot at all times on this wire (when the car is off). I made that mistake once and the small draw will kill your battery in a couple days.

Post 85 - when your efi controller determines that you need the fan, it completes the circuit in the relay and that allows power to flow through to the fan. By putting the manual override before this post, you're completing the circuit and triggering the relay to close.

Post 30 is the power feed that runs the fan. Find out the draw of your fan and make sure the fuse can handle it. Maybe there's a wire in your fuse box called "fan power"...you can use that to run to this post. If not, you can run right from the battery with an inline fuse on that wire.

Post 87 - when the relay circuit is closed by the Post 85 trip wire (or your manual switch), post 87 will send power to your fan.


The same basic principal applies to anything you use relays for (like headlights). Any high draw item should be run through a relay.
 

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Discussion Starter #3
Wow Dan...very thorough... I think I follow. The RF harness has a fan fuse and relay built in. So if I'm understanding you and reading the schematic correctly, the existing "fan" fuse should already be wired into the 30 and the switched 12v already wired into the 86 (on the existing "fan relay". All I need to do is run the "fan 1 relay" wire provided from the EFI harness in to the 85 on the existing relay ( with a toggle wired prior as pictured) and run a wire fron the 87 to the fan and ground the fan?
 

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FFCobra Captain
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I'm not familiar with the RF Harness to say for sure.

Is there a wire in the harness labeled "Fan Thermo Switch"? If so, then you'd probably go from your EZ-EFI trigger wire to that. You might be able to put the fan override switch between those wires.

Then you'd use the Fan Power coming out of your fuse panel to your fan power.

I would definitely confirm with someone else first though.


EDIT...take a look at Jeff's post in this thread...it might help.
http://www.ffcars.com/forums/17-factory-five-roadsters/302911-wiring-questions.html

PM him if it doesn't...he's built quite a few of these cars and will know how to get it done right.
 

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FFCobra Craftsman
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Both the diagrams are the same.
 

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Ryan,
Got your PM. Sorry I'm a little late to the party; I've been painting a roadster since Friday night which has had me pretty tied up.

Looking at the info provided it appears that they are controlling the fan by switching the fan relay ground within the ECU. To marry this with the Ron Francis harness you first need to go to the dash harness and join the brown "fan switch feed" and orange "cooling fan" wires together. This will provide power to the relay whenever the key is on. Next you need to join the green "fan thermo switch" wire from the sending units leg of the RF harness to the blue "fan relay" wire in from the EZ system. This should turn the fan on whenever the ECU calls for it and provides a ground for the relay internally. To add a manual control switch splice into the green "thermo switch"/blue "fan relay" and land both sides of it to the same terminal of an on/off toggle. Run a wire from the other switch terminal to ground. With this done the relay will energize and turn on the fan whenever it gets grounded either by the ECU or manual switch.

Hope that helps!

Jeff
 

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Official OLD GUY
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X2

I concur, Captain . . . the message is authentic.

What Jeff said.

The ECU does ground thing to make them work. Powering the relay coil with switch power will "saturate" the coil and allow it to be controlled by a grounding transistor within the ECU, faster and more efficient.

Doc :beerchug:
 

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Discussion Starter #11
I got everything wired as posted below. Thanks guys. Last question hopefully, at the fan, there are two wires. One blue and one black. I assume I ground the black. What do I run to the blue wire on the fan
 

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I got everything wired as posted below. Thanks guys. Last question hopefully, at the fan, there are two wires. One blue and one black. I assume I ground the black. What do I run to the blue wire on the fan
There is a 3 wire plug in the front harness with a blue wire marked "cooling fan" which will connect to the blue wire on the fan unit. The other (brown) plug in the front harness has a black "ground" wire which gets connected to the black wire on the fan unit. The brown plug also has a black ground wire with a ring terminal on the end---be sure to land this to a good chassis ground point.

Cheers,
Jeff
 

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Discussion Starter #13
Done, thanks. I was having a problem finding the blue and black wires in the front harness because they were still tucked up into the loom
 
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