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2005 Forester XT Auto
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I have read through this many times to understand it better and teach myself a bit about electronics so I can make a video tutorial for my 05 XT. I didn't want to bring this back to life but the original posters have not been active for a while. My question is
1. Which side is the TCM side and which is the Solenoid side?
2. MB stated in his original setup he was going to use a spdt then switched to a dpdt for the light, but there isn't a diagram for the spdt if someone want to do that, is there one out there?
3. Apparently there is supposed to be 12v power supplied for the turbo models, but no one has said what power source they used (possibly heated seats) or the color of the wires/were they are located.
 

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The white/green wire from the solenoid is cut before the TCM, goes through the switching, and then returns via white/green wire, or the white/green wire position at the TCM. On my MY'03 the 12V supply is for the indicator light; I suggest it's the same for the XT.
 

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2007 Forester XT
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Hey Drake,
1. The TCM is the 'plug' end, the solenoid is at the other end of the 'loose' wire (once cut). In the XT I installed this in, the TCM looked like: (the black box bit)
529100

2. I used a double pole switch. I needed to have two actions - power to the Solenoid and resistance to the TCM. This was easily done with a DP switch.
3. I sourced 12v power from the cigarette lighter wiring by piggybacking of its standard wiring. It's decent gauge wire, and designed for a high draw, so taking a little shouldn't matter (in my opinion). But you could source it from anywhere that is handy, suitably sized and easily identifiable. I looked at running a piggyback fuse from the fusebox, but the piggyback I had was too tall to fit in the box.

Hope that helps.
 

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2005 Forester XT Auto
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Great info, I understand which side is which now. I think the cigarette lighter is a better wire than the heated seats. How did you wire the double pole? From what I understand you need to have 12v power running to the TCM when the switch is turned on when the white/green wire is redirected to the resistor.
 

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2007 Forester XT
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For a TURBO Forester, the 12v needs to go to the Solenoid (in order to make it move and lock the transfer case 50:50)
The TCM needs resistance to stop it throwing an error.

The following is relevant to the TURBO setup (but fairly easily modified for a NA engine)

I've tried to step through it in an earlier post (#463 - 4WD On Demand From 4EAT), but the crux of it is:

529110



When the switch is OFF, the COM (common) terminal from each side is connected to the NC (Normally Closed) terminal from the same side. I've connected the Left side NC to the Right side NC. This means that when the switch is OFF, the Solenoid (COM left) is connected via NC Left to NC Right which is connected to the TCM via COM right.

When the switch is ON, the COM is connected to the NO (Normally Open) terminal of the respective side. So when the switch is ON, the Solenoid gets 12v in from the Cigarette lighter circuit (delivered via the switch) and the TCM gets 4 ohms of resistance which then 'leaks' to ground. This is because the TCM is looking for resistance from the Solenoid - if it doesn't get it, it will assume something is broken and throw an error code, causing a light on the dash to come on.

Does that make sense?
 

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2007 Forester XT
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I was just re-reading your question about Single Pole vs Double Pole switches. I think a Single Pole could work for a NA engine, as the Solenoid doesn't require 12v (requires 0v to lock up). Whereas the Turbo engines require 12v to lock, so this power needs to get supplied. I think MB may have gone with the DP approach as it means he could supply (variable) voltage (in the future perhaps) to give him variable lockup.

There would be other ways of making it work for a Turbo engine too, but I found the Double Pole relay was the simplest way for me to understand what was going on.
 

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2005 Forester XT Auto
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Sounds like the easiest way would be to use the DPDT and follow the guide for that. The only thing i'm missing is a resistor, but radioshack went out of business :poop:
 

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2007 Forester XT
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Sounds like the easiest way would be to use the DPDT and follow the guide for that. The only thing i'm missing is a resistor, but radioshack went out of business :poop:
I bought mine off eBay. It was the easiest at the time. I also mounted mine to a heat sink, as they seem to get quite hot.
 

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2007 Forester XT
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Yep - the same - possibly hotter. It has the same amount of energy to turn into heat, and less surface area to cool it. I guess if you had a really big one, you may have a greater surface area than the two smaller ones. But probably the other way would work better- more smaller resistors would probably give you a larger surface area. But then you have the issue of mounting them. I found 2 was a reasonable compromise.
 
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