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Old 10-18-2015, 02:31 PM   #1
Patrick92
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Member#: 330541
Join Date: Aug 2012
Chapter/Region: SCIC
Location: San Diego, CA
Vehicle:
2004 STI
PSM (01G)

Default 2002-2007 WRX/STI Manual Fan Switch Install

So I have searched around and haven't been able to find an actual picture install on how to install a switch in your car to manually turn on your radiator fans... Well I found the wiring diagrams and took it upon myself to help everyone out who has been asking about it.

The main reason I did this was to keep my car cool at the track. When I come up to the tree my IATs were usually sitting around 170-180 and it would just rob me of all power when trying to get a good launch. I tried turning the AC on, tried to just hold the intercooler spray down and nothing was working. With keeping the fans constant I can now sit in stop and go traffic and my IATs will be around 115-122 on a 90+ degree day.

So here's what you'll need:

10mm wrench
12mm wrench
18 gauge wire
Wire taps
Wire crimps
Female wire connectors
Switch of your choice

1. Disconnect and remove the battery from your car.

2. Disconnect and move the washer fluid tank from the engine bay using your wrench.

3. Remove the bottom screw on your fuse box using your wrench so you can move it around and flip it upside down.

4. Remove the small plastic piece that supports the relays from the bottom of the fuse box so you can remove all the relays at once and pull back the black electrical tape to expose the wires.

5. You are going to be tapping into two relays using one wire tap. Here is the relays you are going to tap and the color of the wire... Which is the RED and BLUE.



6. Once you have tapped in, run two separate pieces of wire, one going to a ground of your choice and then one coming off of the tap and going to your switch. I used this as a ground.



7. Have a buddy help you pull the wire through the firewall. I used the grommet going into the driver side firewall to connect it to my switch.



8. Connect the battery, and turn them on for a test! High intake temps be gone!

Enjoy and let me know if this helped you!

Patrick

(The switch will turn on the low speed fans only which is plenty to push out all of the heat and not work your alternator. If you want to be able to kick the fans on high, simply tap into the GREEN and WHITE wires on the sub fan and main fan relays and run it to another switch or a three way switch. You will have to turn the low speed fans on first to be able kick them into high speed.)
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Old 01-27-2016, 08:40 PM   #2
maxxell
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Location: Boca Raton / Miami, FL
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Does this mean that what is labeled as "Subfan 2 Relay" in the engine bay relay harness is actually "Subfan 1 relay"?
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Old 01-29-2016, 03:08 PM   #3
Patrick92
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Quote:
Originally Posted by maxxell View Post
Does this mean that what is labeled as "Subfan 2 Relay" in the engine bay relay harness is actually "Subfan 1 relay"?

What?
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Old 01-29-2016, 03:10 PM   #4
maxxell
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According to the labeling in the fuse box, you've tapped into main relay 1 and subfan relay 2. But that doesn't make sense from the wiring diagram or the result.
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Old 08-01-2020, 12:01 PM   #5
anirban0
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Chapter/Region: TXIC
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WRB

Default Did anybody else do this?

Texas heat is so stupid that even after installing a 600 dollar csf radiator/oil cooler combo my oil temp is still sitting at 120+ degree C for an uncomfortable amount of time on the highway. I should be able to be in 5th gear and doing 90 and keep it at around atleast 115 C. I wish it was lower.

I think keeping the fan on before getting on the on ramp of the highway and keep coolant at 194 F rather than 203F could help.

I want to do this. Did anyone else do this..?

And to the OP, by tapping do you mean you combined the red/blue from both relays then in the same junction a power wire and a ground wire one going directly to the switch and the other going to a ground respectively? Where do the other ends of the redblue wires go? Are you reconnecting those ends back into this junction? Does this disable the coolant temp based operation of the fans meaning do I always have to use the switch to turn the fan on? What about during AC operation?
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Old 08-01-2020, 12:37 PM   #6
Mulder
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15 WRX/05 GTO

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OP last logged in 4 years ago.
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Old 08-01-2020, 02:10 PM   #7
Patrick92
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PSM (01G)

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Still alive. Sold the car a while ago. Anyways, my buddy helping me with this is an electronic technician and did about 50 percent of the install. I wouldn’t have taken the time to write up everything if it didn’t work. I also wish I would have wired it up so I turned on the high speed fan and not just the low. A lot of air movement. This is basically a way to manually turn the fans on. They will still function normally, AC still works and so does everything else. The only other thing I found that you had to do was have your tuner disable the fan circuit codes. They would pop up from time to time.
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Old 08-02-2020, 08:30 PM   #8
anirban0
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WRB

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I am so close to setting this up. Bought a switch that looks like yours. Its two prong but doesnt have the illumination like yours. One pin says power in and other says power out.. which prong do I connect the wire coming out of the wire tap? Do I have to run power to the switch from another 12v source to the "power in" prong? Then connect the wire coming out of the wiretap to the power out prong?
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Old 08-04-2020, 02:17 AM   #9
anirban0
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2005 STI
WRB

Default Got it working!

Just to close out this thread for anyone else wondering. Turns out I didnt need to combine the red/blue of both relays. If you ground either of those two relays it kicks both fans on. I chose the Main relay (closer to the firewall in the pictures above). So split the red/blue wire from that relay and soldered in an extra wire into that and ran it to one of the terminals of a two prong switch then ran another wire from a good ground source to the other terminal of the switch. Turn on switch it completes the ground circuit and turns the fans on. This doesnt interfere with normal operation of fans (kicks on at 205F). This is an amazing mod... now instead of letting the temperature climb upto like 203F while waiting at a red light.. i just let the fans run almost all the time and able to keep it way below that (only drove it at night so far to test and was able to keep coolant temp at 187F which keeps oil temps right at 110C). I just hope this wont have any adverse effects down the line. I welcome those of you with more knowledge on this stuff to chime in! But I just want to thank the OP for this idea! Oh and I also didnt get any CEL.
Next day:
Tested again during the 1pm heat in houston. That heat is brutal. Fans i am sure helped a little but damn.. on the highway doing 90 in 5th gear with 4k rpm nope coolant temp would not come down below 199F and consequently oil temp would not get below 118/119C (measured at oil galley under throttlebody). And yes did get a cel P0691 fan circuit low because i pressed the switch while the fan was already on from high temp. Oh well. I think it still helps.

Last edited by anirban0; Yesterday at 11:46 AM.
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