Jdm Subaru Auto intercooler sprayer. Can it be installed in a 04-07 Usdm STi?
Once again Japan gets all the fancy stuff, don't they? At least when they released the 2004 STI we received a manual Intercooler sprayer. But we could have had so much more, perhaps an Auto sprayer with a 12 L tank ..? Did you know that their Auto sprayer was Ecm controlled as well ..? We will keep it simple and use a boost dependent switch
New to me Jdm auto sprayer button and your standard USDM sprayer button
So that brings us to our topic, how hard is it to add the Jdm auto sprayer button and what else is necessary to make it work. I assume all this could be added to any car, I will be using my 2005 Sti which comes equipped with a tmic water sprayer, being able to add to these wires make this pretty straightforward. If you have the will and determination you could add all this wiring for any other models.
Time frame
Since we are using a 2005 Sti the base wires and components are laid down, we just need to add a couple components and wires. I'd say if you have a good grasp on electrical and electrical installation you are looking at the install taking about 1-2 hours. I might come back and edit this as I was building the process and testing during my install and it took a bit longer than that.
Tools
Fluke dvom
Wire crimpers
We won't use a lot of tools but you do need to have a basic electrical tool set. A meter, wire crimpers, butt connectors, solder, soldering iron are going to be your main tools. A few other hand tools might not be a bad idea.
Parts
Jdm Auto intercooler sprayer switch
Wiring from another Subaru makes this much easier.
Auto sprayer button, hose, and the Hobbs switch shown here.
I'd highly recommend you find a wiring harness for an older Outback/Legacy which is located to the left of the steering column. I found mine a pick and pull in a 2004 model.
How to
Before we start lets answer one question. What's a Hobbs switch you might be wondering? This switch has the ability to open or close due to pressure via a vacuum port on it. The exact Hobbs switch used in this write up is a normally open unit, it can be adjusted between 2 psi to 15 psi and when you hit the set psi it closes the switch and allows power to run through it. Which will then power up the spray timer and run the intercooler water tank pump.
No pressure on the Hobbs terminal and so it is an open circuit.
We add over 5 psi and we now have a complete circuit between the two sides.
First off we will take off the lower trim panel below the steering wheel. On the left side of the vehicle next to the fuse box you will find the wiring for manual sprayer. We can go ahead and unplug the connections and allow the panel to rest at our feet. If you want tot take it one step further you can disconnect the obdII port and remote the panel.
Lonely Usdm button on my 2005 Sti
One plastic screw holds it in place on this side.
The factory Usdm connector and wires to give you an idea of how it is setup.
Next up is finding a good location to either tap into the harness or cut the wiring out so you can tie your new connections in. I went all in and snipped it about 6 inches away from where it tees off as seen below.
Cutting the factory four wire hardness off
Stripped back and ready for the additional wires for the Auto sprayer.
We now need to figure out how we are going to electrical tie in both buttons in. Our goal is to have both buttons available for use. This allows you to both set it in auto mode but also gives you the ability to trigger it whenever you see fit.
This is the wiring harness I found in an 2004 Outback at the junkyard. It is located in the same location as the Sti buttons. This makes wiring this up a breeze.
If we take a look at the Usdm wiring we find that we have a fairly simple circuit. We have a fuse for our power source which runs to the manual button then on to the spray timer and finally it hits the motor where it can supply power and activate it for two seconds. Below is the Usdm wiring that I colored to help you easily identify the main wiring colors running to the switch. I left out the tracer colors as all the wiring utilizes different main colors that are easy to identify
Yellow(YR) is ignition source power for both the switch and the intercooler timer. Red(RW) sends power to the Intercooler timer to power on when the spray switch is pressed. Violet(V) and Orange (OrW) illuminate the button when powered on. The connector number is B294 which is a 6-pin connector visible in the left corner of the diagram. Pin 2 will be Orange, Pin 3 will be Yellow, Pin 4 is Violet, and Pin 5 is Red.
A closer look at the portion of the circuit we will be dealing with.
We can easily merge the wiring to run the auto sprayer but if we look at the Jdm wiring we see the Ecm is part of the wiring diagram. Well there are ways to allow sensor data to trigger the auto sprayer, I am going to take a more simplistic way of firing it off. I am going to simply run a Hobbs switch which will control the auto spraying function.
So now we need to figure out how we can easily merge these two diagrams. The pins on the connector for illumination pins 2 and 4. The easiest first step is to tie the illumination portions(violet and orange/white) of the buttons together, this allows them to shine at night so you can easily identify them.
Check the location of your pins within your connectors. They may be different or you may need to reorganize them.
Make sure your connector has enough pins for the button you have decided to use it on.
Prepping some of the wiring before going into the car. I only use the colors found on the oem harness because your colors liekly won’t be the same.
The next wiring will be to power up the switch, so let's take it to connector pin 5 and connect it to power from the yellow/red wire in our diagram.
With power completed let's get a ground for this switch, we will run pin 1 to your preferred ground. I decided to use a ground right near steering wheel on a bolt. I will likely find a more permanent solution in the future but this takes care of it for the time being.
This is where I ended grounding the circuit for the time being. It’s a perfect good ground but I’d like to clean up the wiring for this.
We need to bring in the Hobbs switch now to be able to control the power through the auto switch. The last pin left is pin 3 so we will take that to the Hobbs switch and the other side of the Hobbs switch will go to the Red/White wire that powers on the auto timer and this powers up the motor.
Now we need to splice in the Auto sprayer with the Usdm wiring. The wiring has been color coated on the Auto sprayer to indiciate where it will be merging to the Usdm wiring. On the 6-pin Auto sprayer connector we will tie in to these points. Pin 1 goes to a chassis ground, Pin 6 is not used, Pin 5 will merge with the (Y) yellow power wire, Pin 3 heads to the Hobbs switch, Pin 4 will merge with (V) illumination and Pin 2 merges with (OrW) Illumination. We have one empty pin on the Hobbs switch so it will complete the circuit to the (Rw) Red wire.
Power source for the Hobbs Switch being put together.
To give the Hobbs switch the ability to close we need to connect a vacuum hose to it. My STi came with the factory Lamco boost gauge which has since be replaced but the vacuum line still runs into the car. Find a easily accessible area to this vacuum line and you will T in to it and run a line back to the Hobbs switch.
Vacuum sourced from the boost gauge hose.
If you don't have a boost gauge you will need to find a vacuum source and a good place to tie in is the bypass valve and run this back to the Hobbs switch.
Before I soldered my wire connections I went ahead and tested that everything was working as I intended. The button’s text should illuminate when your turn on your headlights. When you engage the Auto button you should have an orange light letting you know it's on. After this quick check for operation I decided it was time to finalize my wiring.
Test run before laying down solder.
We have working buttons!
Make sure you slide your shrink tubbing over the wires before soldering. You can also wrap your wiring up for a cleaner look with corrugated tubing or standard electrical tape. I am currently allowing the Hobbs switch to reside in the coin tray in front of the fuse box. I am actively seeking a better way to mount it and will update it in the future.
Solder is applied and it ready for reassembly.
You can now slide the panel back up and place and check once again for proper operation before taking it out for a quick test drive to check that the Hobbs and Auto switch are working correctly.
Everything working as intended!
Congrats on completing this how to! Now you can go look around for 12 L tank to keep your Tmic nice and cool while your heavy foot keeps you in boost!
Amazon parts
Jdm Auto intercooler sprayer switch
Amazon tools
Screwdriver