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Old 09-15-2012, 09:41 PM   #1
PHATsuby
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Default Radiator Fan Issue on STi swap

Hey Everyone,

I posted this in electrical but figured someone with first hand knowledge may be lurking in here.

So I am trying diagnose this issue. my fans turn on when in diagnostic mode(green connectors connected), but they do not turn on when the car is runnning. I hooked up an obd 2 reader and watched the temp go from cool to 220 F and they did not turn on. Both the upper and lower radiator hoses were hot as well so coolant was circulating.

This is a 2006 STi drivetrain swap in my 2001 legacy with a new 2004 baja turbo harness installed and a 2004 STi ecu. In looking at the wiring the ecu pinout is identical on the baja ecu and 04 sti ecu.

fuses are good and the relays are brand new with the harness.

I just don't get what would allow them to work in diagnostic mode but then not turn on when the car is running because the gauge is reading the temp and there is only one sensor so I would assume the ecu should be seeing that exact temp as well if it is reading on the obd 2 as well.

Any ideas would be appreciated.

thanks
Ben
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Last edited by PHATsuby; 09-15-2012 at 09:53 PM. Reason: updated info
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Old 09-16-2012, 12:40 PM   #2
Cougar4
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I believe the ECU uses a second temperture sensor to keep track of the engine temperature that is seperate from the dash gauge. The ECU also controls the fans. You should be able to see what the reading of the ECU sensor is by using your scanner. See if it compares closely to the dash gauge reading. Perhaps the sensor isn't working correctly and it is showing a lower than actual temperture reading. If the sensor is working ok then I would have to think the trouble is within the ECU.

Last edited by Cougar4; 09-16-2012 at 01:17 PM.
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Old 09-16-2012, 12:45 PM   #3
PHATsuby
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Hmm, I'll have look, that is the case on the BE legacies, however I think on the turbo cars it uses a single sensor. at least I'm fairly certain there is only 1 sensor in the crossover pipe, maybe there is one elsewhere I'm unaware of that isn't hooked up. I'll go check that now. thanks

Ben
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Old 09-16-2012, 01:19 PM   #4
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Sensors for the dash gauge usually have one wire and the ECU sensors have two wires.
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Old 09-16-2012, 02:41 PM   #5
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This sensor has 3 wires in the single sensor which I think is the case for all the turbo engines.

I just unplugged the sensor and the fans did turn on and stay on as I think they should. Not exactly sure what that means but I'm going to hook up an accessport and see what is going on.

My concern is that it may be all related to my other illumination issue but I hope not.

thanks for the help.

Ben
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Old 09-16-2012, 04:40 PM   #6
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So I finally married my accessport to my 04 STi ecu so I could do some logging of data. It has radiator fan 1 switch and fan 2 switch as items to log.

So I watched it go to 205 degrees while idling and the fan 1 did start to spin up, then stopped. I checked the fan 1 switch and it was showing a "1" which means it should be on now but it was not. Fan 2 never turned on and the temp was at 215 degrees, I'm unsure if it should have with those parameters but I at least know the first one was supposed to be on and was not spinning(but did for about 1 second).

any ideas?

Thanks
Ben
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Old 09-16-2012, 05:30 PM   #7
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I think the ECU makes a ground connection internally to turn the fans on via a relay. I also think you have pretty much proven the wiring to them is ok since they turn on using the test mode. To verify the trouble is within the ECU you could manually ground the connection at the ECU that goes to the fan relay and see if the fan works that way. If that turns it on then I would have to suspect the ECU needs to be replaced.
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Old 09-16-2012, 07:55 PM   #8
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Quote:
Originally Posted by Cougar4 View Post
I think the ECU makes a ground connection internally to turn the fans on via a relay. I also think you have pretty much proven the wiring to them is ok since they turn on using the test mode. To verify the trouble is within the ECU you could manually ground the connection at the ECU that goes to the fan relay and see if the fan works that way. If that turns it on then I would have to suspect the ECU needs to be replaced.
Good idea, naturally I am now back up in the cities 1.5 hours away from my car and can't test this, I hate my lack of garage right now.

thanks for the help.

Ben
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Old 09-22-2012, 01:37 AM   #9
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Ok so I looked at the diagrams again, the relay setups are different.

here is the STi:


here is the Baja:


So it appears that the Sti is setup for dual speeds where the baja is a single speed for individual fans. This poses a problem I think because when the ecu is telling the fans to run "low" it is only having fan relay 1 triggered, and then on high it triggers relay 2 and I assume turns off 1. But the baja needs both 1 and 2 to be on simultaneously to run both fans I think at a single speed.

I am running a Sti ecu with sti fans but baja turbo wiring. I know people who have run sti ecu's on their baja turbos so maybe the solution is to get baja turbo fans but I don't think the fan itself is different, as the plugs are identical so I theoretically should already be doing that.

Can anyone tell me what to do here? I don't get what the switch is between pins 30 and 33 on the baja diagram are doing?

thanks

Ben
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Old 09-22-2012, 01:02 PM   #10
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While it's a little complicated to see, it appears the Baja fans run at two speeds also. The switch you asked about connects power to the fans either in series with each other for slow speed, or in parallel, for high speed. There should be a connection to power on pin 32 of the relay holder but it wasn't shown. The relay coils are controlled via the ECM by making an internal ground connection to activate the relays.

Last edited by Cougar4; 09-22-2012 at 01:14 PM.
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Old 09-22-2012, 01:19 PM   #11
PHATsuby
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Quote:
Originally Posted by Cougar4 View Post
While it's a little complicated to see, it appears the Baja fans run at two speeds also. The switch you asked about connects power to the fans either in series with each other for slow speed, or in parallel, for high speed. There should be a connection to power on pin 32 relay holder but it wasn't shown. The relay coils are controlled via the ECM by making an internal ground connection to activate the relays.
What is controlling the fan mode relay then? when the Sti ecu is telling relay 1 to be "on" that is when the fans don't run(or actually one tries to then stops), but they run when cycling through diagnostics and when the coolant temp sensor is unplugged, all of those seem to be at high speed I think.

I am just trying to figure out what may be the issue when B25 is grounding, maybe that's the issue that it isn't but I'm also wondering how the mode is determined by the fan mode relay. It may be the issue only when in series vs. parallel? The concerning thing though is still that it didn't kick it over to run high at 215 degrees which in the manual says they should be both running over 212 degrees.

thanks for the help

Ben
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Old 09-22-2012, 02:00 PM   #12
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Just went out and discovered this:

The relay holder has terminals for all those spots


the relay itself only has 4 legs, when I would think it needs 5?


Is this correct? It seems like the wrong relay is in there, I checked all the other relays to see if maybe i pulled them and put the wrong ones back in that location but they are all the same, none of them have a middle pole.

What it looks like is there is no pole going into the terminal for 33 which looks like it controls the parallel vs. series on the fan mode relay?

If it is the wrong relay anyone have an easy source for the correct one?

Ben

Last edited by PHATsuby; 09-22-2012 at 02:07 PM.
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Old 09-22-2012, 10:30 PM   #13
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You are correct Ben, the relay needs to have the extra contact. I assume the relay in there now is a standard Bosch relay and you can also get the version with the extra contact. I would think you should be able to get one just about anywhere the standard model is sold. To verify that the relay is the problem all you need to do is jumper pins 30 and 33 together, which are used for the low speed mode. I would remove the relay and find out which socket pins tie to those wires and put a jumper wire in those socket pins. If the fans now work in the low speed mode you just need the relay. I would suspect that the fans are in the high speed mode for the testing so it appears things are ok. So the ECM just may be ok.

Last edited by Cougar4; 09-22-2012 at 10:39 PM.
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Old 09-24-2012, 12:27 PM   #14
PHATsuby
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I did try a jumper but I only had some little connectors that may have not been making a good connection.

Here are the notes I have in just testing various relays in or out WITHOUT the jumper in place:

With only fan 1 relay in, nothing else. No fans turn on

With fan 2 relay in, fan 2 cycles every time on high happens with just fan 2 in and with both fan 2 and fan 1 relay installed.

With fan mode relay and 1 and 2 installed, fan 2 cycles everytime on high, fan 1 cycles every other time on high.

With fan 1 relay and fan mode relay in, only fan 1 cycles on high every other cycle

With only fan mode relay in, nothing turns on
With fan mode relay and relay 2 fan 2 cycles on high every time.

Does this still point to the fan mode relay being the issue? I feel like it does. I have asked a baja turbo owner to pull their relay to confirm the 5 poles before I order one from subaru.

Ben
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Old 09-24-2012, 05:44 PM   #15
Cougar4
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It's a series circuit when the fans are in the slow speed mode. If you break a series circuit at any point in the circuit then nothing in that circuit will work because current can't flow through the open connection. No relay pin connection to complete the circuit....no function.

You should be able to get a relay from any parts store but perhaps these are special. If you can't get one there you should be able to get one at a salvage yard.

Last edited by Cougar4; 09-24-2012 at 05:50 PM.
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