How to Override your cooling fan

About This How-to
Author: moonwell
Added: 06.05.01
Updated: 03.07.04
Discuss (48)
This how-to shows you how to install a switch to turn on your cooling fan whenever you flip the switch, while still having it behave normally when the switch is off. This is a good mod for keeping your engine cool during, after and between racing for slightly faster, more consistant times. Keeping the engine cool also causes less wear on its compnents.



How To Do It

Step 1

Locate the Cooling fan relay. It is a small black box clipped to the inside of the drivers side fender, near the battery. It has about 5 wires coming out of it, covered by wire loom. See the pictures below for the exact location.

fan fan

Step 2

Now that you have found the relay, peel back some of the wire loom to expose the wires inside. Locate the green wire with the white stripe on it. This wire is what we are looking for.


Step 3

You may wish to disconnect the battery before beginning, since you will be dealing with the electrical system, but then you have to deal with the pesky idle relearn for the computer. I didn't disconnect my battery and didn't have any problems.

Using a sharp knife, carefully cut off a section of the insulation from this wire. You do not want to cut all the way through it (although, it isn't that big of a deal if you do), you just want to expose enough bare wire to solder another wire to.


Step 4

Now, take the wire that you bought, strip off about a half inch of insulation from one end and twist it around the exposed part of the green cooling fan wire. To be safe, you should secure this connection with a little solder.

Close off the connection with some electrical tape, and put all the wires back into the wire loom.

Step 5

Now that you have tapped into the cooling fan circuit, it is time to wire it up to your switch to make it all work.

You can mount your switch anywhere you wish. The most convenient location, is of course somewhere on the dash. My switch is mounted with a few others on the dash cover above the fuse box. A picture of the location is shown in the final step.

Step 6

In order to mount your switch inside the car, you must drill a hole in the firewall to pass the wire though. I used a hole that I had drilled earlier for my amp power cable. If you need to drill a hole, start out with a small bit and work your way larger. You may wish to run other wires though this hole in the future, so make it plenty large. And don't forget to put a plastic or rubber grommet in the hole, so the bare metal does not rub through the insulation on your wires.

You will need to remove both under dash covers using a 7mm socket to get access to the firewall behind the dash to run your wire though.

The pictures below show the location of the hole I drilled in the firewall. You want to make sure you don't drill into anything important on the other side! The left picture shows the hole location from the outside, while the right picture shows the hole from inside, under the dash.

fan fan

Step 7

Fead the wire though the hold in the firewall. Once it is routed though, install a crimp on female blade connector to the end, to make it attach easily to the switch.

Cut off another short length of wire to use as your ground wire. Attach a blade connector to one end, and a ring connector to the other, so you can screw the end down to bare metal to ground the connection.

It is your choice where to mount the switch, so mount it, then connect the live wire, and the ground to the switch, and secure the ground wire with a screw to a clean metal surface under the dash. You can use an existing hole, or drill your own. The hole I used also ground a few other components, such as my alarm.

DO NOT hook the switch up to a power source! You are making the cooling fan come on by grounding the relay, not by providing direct power to the fan. If you hook the switch up to the battery, you will fry the relay!

fan fan

Step 8

Before you put everything back together, test it out to make sure it is working. Turn the ignition to the run position (not acc.), or start the car. Turn the switch on, and make sure that the fan comes one.

If all is good, reassemble anything your took apart in the dash when mounting the switch. If it doesnt work, check all your connections and be sure you have a good ground.


Step 9

Now you can keep your engine cool whenver you want to. Whether it be in traffic, or at the racetrack. This mod does not affect the stock behavior of the cooling fan when the switch is off, so the fan will still go on and off automatically when the switch is not in use.


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