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2004 STi
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Discussion Starter #1 (Edited)
Wonder if anyone else has encountered this issue, its a bit of a headscratcher, the heater panel and heater/aircon keeps switching on/off but its not always that consistent. At first I'm thinking water ingress because during the summer, if it didn't rain it would work 90% of the time but this wasn't always the case...

So usually upon first start the heater control panel does nothing, changing any of the fan speeds, temps, pressing the ac or the heated screen has no response or lights. Drive for about 10-15 minutes and you'll hear an audible click (sounds like a relay, I've swapped what I thought is the right one but I think I'm maybe wrong) and it comes on, often for a matter of seconds and then its off again it will do this on/off for the next 10-15 minutes or so and then sometimes, but not always, it will stay on and work for most the journey but then sometimes it will still trip off and on now and again (if you watch it the the air con on you'll see the compressor spin up and switch off as it clicks on and off).

In Scotland, we got up early to drive back (10hr trip) and it was proper chucking it down, for the first 45 minutes absolutely no heating worked and the windows were steaming up as a result, as it was pitch black and 6am in the morning, seeing luv all was a big issue. After about an hour of driving with the windows cracked and stopping to wipe the screen we went through a massive huge puddle on the left side, proper wave of water coming up... could be coincidence but instantly the heater came on and started blasting out the heat it set at. A few minutes later it went through the usual ticking on and off until it either says on or stays off.

I've had a couple of goes at trying to find the problem with this to no avail, I've had the circuitboard for the panel out to inspect and cant see anything visible problems on the board (see pics) and the connections are seating well, I've followed all the wiring back to the matrix behind the glovebox etc to see if connections are seated and it is. There is a turbo timer and a jdm toll card reader wired into the car and it doesn't exactly look pretty so I was thinking a dodge earth but it was working fine for about a year or so before it starting doing this. Also, I haven't really got any wiring diagrams to go off and not entirely which fuse/relay does what but they don't appear blown (and if they were it would stay off right?).

We do maybe 5k a year, had the car since 2018 and the aircon when it works blows cold and I'm pretty sure the heater panel would work if it just needed a regassing. Its a weird one, if the panel was completely dead then it would be obvious but the fact when it on it work absolutely fine so this behaviour is really confusing. HALP PLS! :)
 

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Don, King of the parts diagram
MY11 WRX STi Sedan 6MT
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5,832 Posts
Having compared EDM and JDM part numbers the closest is the auto A/C unit fitted in the UK MY06 versions
Having checked the US version and compared other models there doesn't appear to be any cross links into the Body Integrated Unit as yet (MY09 onwards there is )

MY06 AAC wiring
MY06 AAC1.JPG MY06 AAC2.JPG MY06 AAC3.JPG MY06 AAC4.JPG
In case it helps attached are the self diagnosis procedures
 

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Discussion Starter #3
Is it just me or does that make for very difficult reading? I'm struggling to figure out where the relays it refers to are. I can see there are some to the left of the under drives dash and also under the bonnet. All of them have had a stiff tap but no change. I've pulled most/all of the dash fuses to check for any that are dead, there seems to be a 15 amp with a peice of wire soldered onto it thats just hanging around, its always been like that though. I haven't got a full picture but it is a bit of a rats nest along with the jdm turbo timer and car reader wired into everything.

Whilst its never a good idea to just chuck money at ebay electrical parts, I'm tempted to buy a new a/c panel board just incase its that at this point.
PXL_20201120_112346410.jpg
 

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Discussion Starter #5
Im not saying its the same in any way but my heating, fan and ac stopped working recently and i replaced the control dials unit which fixed the problem.
Noticing that a few of these have sold on ebay previously, I'm thinking its common. I should have bought them ages ago only issue is I can find a perfect matching part number at the moment sadly. Not sure if there is a difference between the zenki/kouki heater circuit maybe other than fitting....
 

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Don, King of the parts diagram
MY11 WRX STi Sedan 6MT
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5,832 Posts
Forester STI HVAC controls - Revisions C & D 72311SA100; Revisions E & F 72311SA140

I'm struggling to figure out where the relays it refers to are
I hope this helps ;)

By using the plug identifiers (eg B50; F27 ) from each individual system diagram, you can find where they (the plugs) are in the car.

Loom plug identifiers:
B - Bulkhead; F - Front; E - Engine; I - Instrument; R - Rear; D - Door; T - Transmission; AB - ABS

UK MY06 Front Loom; Bulkhead Loom in Engine compartment; Bulkhead Loom in compartment.......
Capture1.JPG Capture2.JPG Capture4.JPG Capture6.JPG Capture7.JPG Capture8.JPG Capture9.JPG Capture10.JPG Capture5.JPG Capture3.JPG
 
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Don, King of the parts diagram
MY11 WRX STi Sedan 6MT
Joined
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5,832 Posts
Plus the Engine Loom.......
e1.JPG e2.JPG e3.JPG
Instrument Panel loom
i1.JPG i2.JPG
 

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MY04 FSti MT6
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490 Posts
A question for you @batou - when it's playing up, do the push switches on the the 3 controls (rear demist, recirc & AC) illuminate when pressed?
 

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Discussion Starter #9
Thanks Don, that makes much more sense now I can see where things go :)

A question for you @batou - when it's playing up, do the push switches on the the 3 controls (rear demist, recirc & AC) illuminate when pressed?
If its tripped off (at the moment when you turn the car on it always is) no, it is completely dead, doesn't respond to the diagnostic mode either. When/if it finally trips on it will light up and all of the fans work, heat blows out of ac blasts cold air perfectly until it trips back off.
 

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So first thing to do obviously is to check that +12V is getting to the control panel using Don's excellent info. If it is, then putting my electronics hat on likely scenarios for the whole unit tripping on and off are either the microcontroller IC (64 lead square thing top L) throwing a wobbly or the 5V regulator IC2 which powers the microcontroller.
 

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Discussion Starter #11 (Edited)
Firstly, this thread can now be updated to SOLVED. With some useful info for FSTi owners...

So coming back to this, the control unit was getting power when I checked but as discussed nothing was lighting up or working on the control panel, sometimes it would come back to life but it would trip on and off. The part numbers for the Forester STI HVAC controls as Don suggested are as follows: Revisions C & D 72311SA100; Revisions E & F 72311SA140

Now I was curious, there was one for sale on ebay for £142 with part number 72311SA140, mine is 72311SA100 and the pastic housing is different, but... what I noticed is the climate control unit for other SG9 foresters looked very similar just with different part numbers, some of them had the same orientaion as the STI controls but different colours in similar housings. I took out my control unit and dismantled it and its literally just a circuit board inside which the control knobs interface with. This got me thinking, so I decided to take a punt on a similar set of controls from a 2005 Forester with climate control on ebay for £25 with similar housing as mine. I couldn't see the part number on the advert but when it arrived its 72311SA070. Anyway, I took it apart and compared it to the one out of my FSTi and this is what I found...
PXL_20201126_164513055.jpg
As you can see below the circuit board part numbers are identical, on closer inspection of the front and rear I could find no difference at all.
PXL_20201126_164518689.jpg
And as you can see on the rear housing it looks that because they are almost identical they had to mark the STI ones with a pink pen on the production line to easily spot the difference...
PXL_20201126_164237773.jpg
Anyway, I put the "new" circuit board in my STi housing, fitted it back into the car and started the car up and everything works perfectly now. Aircon, demister, heat etc. Pretty happy considering I save £117 by not buying the only STi one on ebay! I'll keep an eye on this over the coming weeks and see if it remains working and report back but for now it appears to be resolved :)
 
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