Now it's time to track down the wire that carries the TCM signal to the solenoid. Back to the FSM:
We're looking for the AWD transfer solenoid which is called the "Duty Solenoid C" in my manual. As you can see, it can be found at terminal 15 of connector B54
Looking at the layout of the B54 connector, we see the physical location of pin 15
So, where exactly is this connector located in the car? Well, it's on the TCM. Which you'll find mounted just to the left of the steering column. Crawl into the driver's side footwell and look up, you'll see it. Here are some pics to give you an idea of what you're looking for. Note the orientation of the brake pedal to get your bearings
One quick note: I highly recommend one of these -
It's much easier to do a job like this in tight quarters when you can use both hands and not have to dick around with a work light.
Ok - so the connector we're interested in is the white one (located closest to the firewall). We've seen the location of the wire on the connector diagram of B54, so we should be able to just cut it and be on our way right? Be my guest - but I like to be dead sure when I cut wires, so some diagnostics are in order. A look back at our diagram shows some tests we can do to verify we've got the right wire. This is an important step because it appears that turbo models use a different wire.
According to the tests procedures - we need to install the FWD fuse and turn the ignition to "on". The FWD fuse is located in the engine compartment fuseblock.
Remove the lid and locate the FWD fuse position
Unless your car is drastically different, the fuse probably goes here:
Spares are kept in the lid. Install the one of your choice - I used the 10 amp with no issues.
On to the connector - I've removed the connector for clarity, but this whole job can be done without ever pulling the plug. In fact the plug has to be in place to do the tests.
With the plug in place, and the FWD fuse installed, turn the ignition to "on" but don't start the car. Jam one of your multimeter probes in the back side of the connector (in the appropriate terminal of course) and the other to a good ground; usually some bare metal of the car chassis. My meter has pretty long leads, so I ran the negative probe out to the factory ground points in the engine compartment.
When done properly, you should get 8.5 volts or more. If your meter is like mine, the probes are too fat to get into the connector, so you may have to jam something metal in there to get a decent connection, and then touch your meter probe to that to get the reading - I chose a small pick.
Now, remove the FWD fuse, put the gear selector in 1st, fully open the throttle, and repeat the test. This time, you should get less than .5 volts. If this checks out, you've got the right wire. If not - use the wiring diagrams and diagnostic sections of your FSM (you did dowload one right?) to troubleshoot and track down the right wire.
If you get totally stuck, post here and i'll try to help as best I can.
Now it's time to cut the wire. Dig a few inches of wire out of the harness and snip it.
Now we can extend the wire out to the switch. I located mine back near the handbrake, but you can put yours wherever you like. Just splice two lengths of wire to extend each side of the white/green wire to your switch location. Solder and heatshrink the connections.
Now route your extended wires to your switch location. If you're planning to put your dummy load in the footwell, You should route your new wires, AND an additional piece of wire of equal length - this will be the wire that feeds the dummy load from our switch (more on that later). If you'd rather put the dummy load elsewhere, you're on your own. Not because I don't like ya, just cuz I didn't do it that way.
Alright, we've got our wires pulled to our new switch location, so it's time to wire up the switch. Let's talk a little about the particular type of switch we're using. I've spec'd Single Pole, Dual Throw (SPDT On-On) switches because they allow you to switch between two different circuits - which is exactly what we want to do here. When the switch is in one position it's like nothing ever happened. The TCM signal flows, unaltered, through your new wires, through the switch, and on to the solenoid - all you've done is made the trip a little longer. But, when we flip the switch to it's second position, the signal will now flow through the new wires, out to the switch, but now the switch will redirect the signal to the dummy load that you built. Very simple, yes?
Looking at the switch, you'll see three posts; they should be labeled as COM, 1, and 2. On my particular switch, the center pin was COM, and 1 & 2 were the outer pins. In order to understand what the switch is doing, you can visualize the pins as "Ins and Outs". Think of the COM pin as your "In" and the 1 and 2 pins as your "Outs". The signal will always enter through the COM pin, but where it exits is decided by which "out" you have selected with the switch.
The first step is to set up your "In" to the COM pin. Since this is the signal that feeds the switch, you need to make sure that you connect the wire that's coming FROM the TCM to the COM port, otherwise, you won't have a common signal and the switch will only work in one position - not good.
One quick common-sense note before we whip out the soldering iron again....unless you're getting all crazy, and wiring up a quick release connector before your switch, you should have your wires pulled through your switch mounting hole before you wire it up. Trust me.
Ok - let's melt some solder!
Solder/heatshrink your TCM signal wire to the COM pin. Then solder the wire that goes to the solenoid onto pin 1. Now you have a complete circuit....that does absolutely nothing special.
Now we'll wire the dummy load to pin 2 - you know what to do.
You may have noticed that my COM wiring changed between those two pictures. I have a very simple explanation; I screwed up the first time. The picture with all three wires is my final configuration (the big fat wire is my COM wire). Multicolored wires would come in handy to avoid screwups like that, and I'll probably rewire everything when the weather warms up. Since I didn't know if this would even work, I was just scavenging wires from old, blown DC wall transformers.
Wiring the 1 and 2 pins is up to your personal preference. I chose pin 1 as my "off" position - meaning that the car behaves normally when the switch is in this position. Conversely, pin 2 is my "on" position and is wired to the dummy load, thus activating the 50/50 torque split. How you do it is entirely up to you.
All that's left is to wire up and mount the dummy load:
Solder the wire from pin 2 to one side of the dummy. From the other side you'll run a wire to ground.
I chose to go through the firewall and hook into the OEM grounding points located on the driver's side strut tower. No pics cuz I'm lazy. I'm sure you can figure it out.
Not knowing how much heat the resistors would generate, I chose to temporarily mount the dummy load directly to the TCM. I assumed that since this feature will mostly see use during the winter months, I'll already have the blower on in the footwell, and that should move enough air to keep things the resistors cool. I used a small piece of rubber between the dummy and the TCM to provide both vibration damping, and electrical insulation.
Well, that's about it for Phase 1. I'm still working on installing an LED to indicate when the AWD is locked, and I'll write that up when I get it installed.
But for now, I suggest a little testing before you fire everything back up. Namely, test the switch to make sure it's doing what you want.
With the key on, and the switch in the "normal" position, there should be no voltage present across the dummy load. Flip the switch, put the car in 1st and open the throttle 100%, and you should get around 8.5 volts. If it checks out, you're good to go. Clean up, and go for a test drive.
On the test drive, take the car to a patch of dry pavement where you have enough room to slowly drive a complete circle. With the switch in the normal position, you should be able to drive the full 365 degrees with no problem. Now flip the switch to activate the lock, and try the same circle - you should feel a binding within the first 45-90 degrees. When you feel it bind - STOP and deactivate the lock. You should hear a "thunk" and feel the tension release. If so, pat yourself on the back - you've got full-time AWD at your control. Now - go play in some slippery stuff.
Days like this are when the system really shines:
I need to give credit where credit is due. Big thanks to MountainBiker, Zhe Wiz, SeaComms, and Kevin over on www.subaruforester.org
. This thread
was instrumental in giving me the idea to put this mod together.
Next installment - the handbrake mod. (insert evil laugh)