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  #1  
Old 08-12-2009, 05:42 PM
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Dessertrunner Dessertrunner is offline
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Wiring between ECU & enviro system.

As part of the new install of the Wolf ECU we need to find out how the ECU talks to the enviro system, it appears to have to data wires but the manual doesn't tell us anything.
Can anyone shed some light on this one please.
Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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  #2  
Old 08-13-2009, 04:49 PM
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b3lha b3lha is offline
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Re: Wiring between ECU & enviro system.

Hi Tony,

It is not something I have really investigated.

I know that the A/C signals the ECU when the clutch is engaged so that the ECU can adjust the idle speed to compensate for the increased loading on the engine. I have seen this in the ECU software.

I believe there is also a signal in the other direction from the ECU to the A/C to shut off the A/C at WOT for better acceleration.

I don't think the wires carry "data" in the computer sense of the word, just simple on/off signals. I keep thinking that I've seen something about it in the service manual. I'll check this weekend and get back to you.

Phil.
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1992 Alcyone SVX Version L
1992 Alcyone SVX Version L
1994 Alcyone SVX S40-II
2004 Subaru Legacy 2.5 SE Sports Tourer
1996 Subaru Legacy 2.2 GX Wagon
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  #3  
Old 08-13-2009, 09:50 PM
NiftySVX NiftySVX is offline
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Re: Wiring between ECU & enviro system.

The computer will override the A/C on request also if the coolant temperature is above a set point, if the rpm is too low, and at wide open as already mentioned. I second the assumption that the wire is just either on/off signal, most are this way.

I don't have my FSM handy but many vehicles in fact use the ECM to actually switch on the Magnet clutch relay based on a "a/c on" request from the climate amplifier, so it may operate backwards from what has been suggested, but I am not sure. A wiring diagram for the a/c circuit would reveal this if it was the case.

Also, the cooling fans are switched on by a pressure switch in the a/c hose. This pressure switch may have an interaction with the ECU so that it can help decide fan speed (Hi, med low) depending on a combination of the engine coolant temp and the position of the high pressure switch. (for example, engine temp low, high pressure switch on-> fan med and, conversely, high pressure switch on coolant temp high -> fans high).

These are a couple guesses as to what is being communicated, I am curious to this as well and plan on looking at the diagrams tomorrow as my car is currently at the shop and the manuals are in the seat
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Last edited by NiftySVX; 08-13-2009 at 09:59 PM. Reason: addition
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  #4  
Old 08-15-2009, 06:36 PM
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Re: Wiring between ECU & enviro system.

The AC compressor is a able to be adjusted as it is a variable rate compressor the ECU turns the clutch on and off but the Enviro unit controls the load. The ECU does tell it a number of things such as to unload when the car is a full power etc.
It seems that I may have to put a scope on it to find out the real story, kind of feel its a lot more complicated then I orignally thought.
Tony
__________________
1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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  #5  
Old 08-16-2009, 05:03 PM
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b3lha b3lha is offline
Phil & Belha
 
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Re: Wiring between ECU & enviro system.

I know this doesn't help much, but several years ago, I was doing some work on a JDM SVX owned by a friend of mine. I found the wiring between the ECU and the A/C had been modified by the previous owner. But I never figured out why. This is what I posted at the time.

Quote:
Originally Posted by b3lha
There are some wires that run from the aircon system to the ECU. The brown wire connected to pin 19 of connector B59 has been cut. It's the wire labelled a19 in the service manual, the top connector on the ECU.

The ECU side of the wire has been connected to the 12V supply of the fuel pump relay.

I'm guessing that in some circumstances, the aircon signals the ECU by dropping this line to ground. But I'm not sure what the significance of that is. Whoever did this mod evidently didn't want the ECU to receive this signal.
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1992 Alcyone SVX Version L
1992 Alcyone SVX Version L
1994 Alcyone SVX S40-II
2004 Subaru Legacy 2.5 SE Sports Tourer
1996 Subaru Legacy 2.2 GX Wagon
1988 Subaru Justy J12 SL-II
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  #6  
Old 08-22-2009, 01:56 AM
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Dessertrunner Dessertrunner is offline
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Re: Wiring between ECU & enviro system.

Thanks Phil,
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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