When I took the Shelby to the track (1/4 mi.), I found that water in the aftercooler reservoir never cooled of while sitting in the lanes. One of my many admirers (OK, the Shelby’s admirers) pointed out that the car had to be moving to cool the coolant. So, after a run, I went out and drove around the facility to help cool it off some. I picked-up a solid 2 mph the following run. I wasn’t completely satisfied with that, and thought I could do better with a fan override. I had previously done this on my ’96 GT with good success. For this procedure you will need the following:
o 18 ga. or 16 ga. wire, approx. 3 feet (More if you put your switch farther away.)
o Wire taps (18 or 16 ga.) – 2
o Electrical tape
o SPST switch
o Ring terminals – 4
You will also need 7mm, 8mm and 10mm sockets, ratchet and possibly a short extension. You will also need wire a stripper/crimper tool and a razorblade.
Please allow me to apologize in advance for a couple of blurry photos. My camera has a hard time focusing in low light and I was running low on battery, so I didn’t take multiple shots of each difficult angle. You can still see what needs to be seen. Here we go.
After opening the hood, remove the negative lead from the battery. Locate the power distribution box and remove the cover. You will also notice a smaller auxiliary box on the strut tower, yellow arrow.
Go ahead and remove the top from this one, too. Remove the 8mm-head screws (blue arrows) attaching it to the tower. While you have the ratchet in your hand, remove the 10mm power lead bolt (purple arrow) and the cable from the box. Unscrew the two 7mm bolts (green arrows).
These bolts retain large plugs on the bottom of the fuse/relay buss. Do not try to remove them.
Once the aux. box is free, flip it over. Remove enough of the tape on the harness to expose about 2” of wire. Locate the blue/yellow wire in the bundle. (Orange arrows) This is the aftercooler pump control wire that goes to the PCM. What we want to do is provide an alternate ground path that we can manually control.
(For those of you who don’t know, the PCM controls motors, solenoids, etc. {load} by grounding a circuit to complete it. Once this circuit is complete, the relay that the circuit is wired in series with, opens or closes providing the desired action to the higher current load. This way, a PCM can use a small wire/low current to operate a large wire/high current load.)
Install the wire tap with your new wire. (Green arrow) Tape it all up for the first few inches and remount the aux. box.
Moving over to the distribution center, locate the clip at each end. (Green arrow) Lift the tabs enough to disengage them and separate the buss from its lower housing.
This is a little tricky because the harness is quite stiff. Take your time and lift it up 2-3”. As you lift the buss up, the front black plug should stay in the base. If you have difficulty, that plug may need to have the retaining bolt loosened more. The green plug (red arrow) should lift up with the bus, but be loose.
From this plug, find the purple/green wire in its harness. This is the PCM wire for the high-speed fan. Wire tap this wire and add the other end of your new wire to the tap.
You can route this new wire in the lower housing under the buss to have it come out near the aftercooler pump wire you’ve already added.
Replace the green buss plug. Gently replace the buss onto the lower housing. Tighten the two 7mm bolts and reseat the buss to the lower housing. Replace the power cable and its 10mm bolt.
From here, I wrapped the wires to existing harnesses until they converged. From here, wrap them to our desired length for your switch. (Red arrow)
Cut the two wires to length. Attach an appropriate ring terminal to them for your switch. Create a short jumper wire for the other pole of the switch and ground. (Yellow arrow) I also made a little switch housing. (Purple arrow) This one is my second attempt. I think I plan to make another with a bit more space between the terminals and the ground. Go ahead and connect the ground wire to your ground and the switch. Mount your switch as desired.
The way this works is:
The override only functions when the ignition key is in the “run” position. If you leave the
Switch on for 20 min. you will drain the battery enough so that the car will not start. (You can bump start it, though) You really only need to run these for 8-9 min. before the coolant returns to ambient temps. After a run, I return to the pit lanes. I lift my hood and turn on the switch. After the coolant returns to ambient, I shut-off the ignition, leaving the fan switch on. When the racing comes back to my class I close the hood, leaving the switch on. This way I know that the coolant will be a s cool as possible when I get to the starting line. I picked-up 7 mph in the ¼ mi with this mod. That’s about 35-40 hp (if I remember correctly.) Overall it’s a simple mod that is VERY effective. I think you could use it on an open track event, too. The PCM would almost always have them running, anyway. Good Luck.
