Zeky Posted April 9, 2005 Share Posted April 9, 2005 Hi guys, my 92 Legacy main fan wont start so car is overheating.I checked the fan end is OK.I try bypass the main fan relay and it works. If i connect pins 3 and 4 (the pic)fan starts rights up - thats normal. But if i bypass minus right from battery to pin 1 (or 2 not shure right now) the fan starts too.... so is that normal? What is switching relay to ON ?The coolant temperature sensor?But the temp gauge in dash works fine.... Any diagrams of it?Eny experience? Thanks in advance.... Quote Link to comment Share on other sites More sharing options...
Legacy777 Posted April 10, 2005 Share Posted April 10, 2005 The ECU turns the fans on. If you put 12v on pin 1, and pin 2 to ground.....and the fans work, the relay is good. I would verify the wiring going to the relay. You can find wiring diagrams here http://www.main.experiencetherave.com:8080/subaru_manual_scans/1992_FSM_(Engine_%26_Electrical)/ Quote Link to comment Share on other sites More sharing options...
Zeky Posted April 10, 2005 Author Share Posted April 10, 2005 If you put 12v on pin 1, and pin 2 to ground But i just put ground to it and it work, so maybe some bad grounding i guess... thx for link Quote Link to comment Share on other sites More sharing options...
blitz Posted April 10, 2005 Share Posted April 10, 2005 But i just put ground to it and it work, so maybe some bad grounding i guess... thx for link Not necessarily... You'll need to consult the diagram for your vehicle in order to determine whether the ECU completes the circuit by switching the hot side or the ground side of the relay primary. I'll agree with your assesment that bad wiring would be the first thing to start tracing down. Check the diagram first, it'll save you a bunch of time. Quote Link to comment Share on other sites More sharing options...
Tiny Clark Posted April 11, 2005 Share Posted April 11, 2005 Usually, the ground side is the switched side. 12V is fed to one side of the relay and it awaits a ground to complete the circuit. On some cars, the ground is supplied directly by a thermal switch. Apparently, as Josh POINTED OUT, on your car the ECU supplies the ground. Download the diagram at the link he posted and go from there. Quote Link to comment Share on other sites More sharing options...
Zeky Posted April 13, 2005 Author Share Posted April 13, 2005 You can find wiring diagrams herehttp://www.main.experiencetherave.com:8080/subaru_manual_scans/1992_FSM_(Engine_%26_Electrical)/ Hi ,didn't have time to post here sooner.I just realized mycar is 91 ..my bad So those diagrams will not work for me or will they?.... I am getting crazy realy ,i have been jumping around the car with multimeter all weekend and no luck.... :-\ Quote Link to comment Share on other sites More sharing options...
Cougar Posted April 13, 2005 Share Posted April 13, 2005 I too think you will find out that the ground side of the coil is controlled by the ECU. The sensor that tells the ECU to switch the fan on is different than the sensor for the gauge I think. It may be located in the radiator. Quote Link to comment Share on other sites More sharing options...
SevenSisters Posted April 13, 2005 Share Posted April 13, 2005 Find the thermoswitch (one for ecu), unplug it, jump the two pins on the connector, and see if the fan starts. Quote Link to comment Share on other sites More sharing options...
Legacy777 Posted April 14, 2005 Share Posted April 14, 2005 Those diagrams should give you an idea of how things are layed out. The pin numbering may be different, but it'll give you an idea on where to look. Just pull the connector off the coolant temp sensor, the ECU will see that as a fault, and turn the fans on. If they don't both turn on, you've got a wiring issue somewhere from the ECU to the fans. First check that the signal is being sent from the ECU to both fan relays. Once you've determined that, and swapped relays between the two fans, to make sure the relays are good.....then you'll need to trace your wiring after the relay. Quote Link to comment Share on other sites More sharing options...
Gnuman Posted April 14, 2005 Share Posted April 14, 2005 I too think you will find out that the ground side of the coil is controlled by the ECU. The sensor that tells the ECU to switch the fan on is different than the sensor for the gauge I think. It may be located in the radiator. IIRC, both sensors are located in the coolant crossover pipe (ubnder the intake manifold). The one to the temp gage has one wire, and the one to the ECU has two or three, I think. They are right next to each other, on the passenger side of the TB Quote Link to comment Share on other sites More sharing options...
Cougar Posted April 14, 2005 Share Posted April 14, 2005 Thanks for the clairification about the location of the sensor Gnuman. Quote Link to comment Share on other sites More sharing options...
Legacy777 Posted April 14, 2005 Share Posted April 14, 2005 http://www.main.experiencetherave.com:8080/subaru/images/injectors/DCP_2477.JPG Quote Link to comment Share on other sites More sharing options...
Zeky Posted April 14, 2005 Author Share Posted April 14, 2005 Oh yeah,Thanks guys u are right and the picture clear it all up.But i knew where the sensor is but didnt knew there are two..... So if i unplug the 2wired one no fans start up.Just engine change RPM fluctuating for a while but then stabilize.If connected back do the same.This means that sensor is working i guess.So i am going to study wires diagram and find the right damm wire.By the way where is ECU located. PS.A/C turns both fans on?My do. Quote Link to comment Share on other sites More sharing options...
Gnuman Posted April 14, 2005 Share Posted April 14, 2005 Oh yeah,Thanks guys u are right and the picture clear it all up.But i knew where the sensor is but didnt knew there are two.....So if i unplug the 2wired one no fans start up.Just engine change RPM fluctuating for a while but then stabilize.If connected back do the same.This means that sensor is working i guess.So i am going to study wires diagram and find the right damm wire.By the way where is ECU located. PS.A/C turns both fans on?My do. The ECU is located under the dash, to the left of the steering column. it is pretty far up and a bit hard to get to. Yes, the A/C turns both fans on, to force air over the condensor (which is in front of the radiator) Have you checked the relay that turns on the fans at the fuse box under the hood? Quote Link to comment Share on other sites More sharing options...
Legacy777 Posted April 14, 2005 Share Posted April 14, 2005 If you unplug the two wire coolant temp sensor, the fans should come on. pic of the ECU http://www.main.experiencetherave.com:8080/subaru/images/ecuhide.jpg Quote Link to comment Share on other sites More sharing options...
Zeky Posted April 15, 2005 Author Share Posted April 15, 2005 OK,now thanks. 2 Gnuman.Yes i did checked relays ,they are fine. 2 Legacy777 thx for the pic will be the hell to get to it.And no unplugin the sensor doesn't turn any of fans on. I'll post the progress... Quote Link to comment Share on other sites More sharing options...
Zeky Posted April 16, 2005 Author Share Posted April 16, 2005 Hi guys,need u again.Where is the MPFI unit located i did seach forum but no luck.The diagram shows that the wires from relays goes to the MPFI... Thanks in advance Quote Link to comment Share on other sites More sharing options...
Cougar Posted April 16, 2005 Share Posted April 16, 2005 It should be under the dash near the steering column. Look for metal box with several plugs tied to one end of it. It is mounted on the firewall. Quote Link to comment Share on other sites More sharing options...
Zeky Posted April 16, 2005 Author Share Posted April 16, 2005 It should be under the dash near the steering column. Look for metal box with several plugs tied to one end of it. It is mounted on the firewall. OK,now Legacy777 posted me this http://www.main.experiencetherave.com:8080/subaru/images/ecuhide.jpg and there is not a MPFI.So i dont know. And if anybody know where is this DIODE located(red circle) ,it will be great. Quote Link to comment Share on other sites More sharing options...
Cougar Posted April 16, 2005 Share Posted April 16, 2005 Just curious, why are you looking for the diode? Quote Link to comment Share on other sites More sharing options...
Tiny Clark Posted April 17, 2005 Share Posted April 17, 2005 If you are talking about the main fan relay in the fuse box at the upper part of your diagram, it looks to me like it gets the ground from the pressure switch. The only pressure switch I know of is in the A/C system. Unless they are calling the A/C on switch a pressure switch. Cougar, I can't figure out what the A/C short connector is for either, maybe testing? Doesn't make any sense anyway, since those two lines are shown connected together down below. Zeky, the diode just isolates the ACC hot power and the power from fuse 13, and would affect the sub fan. I hate subie diagrams. Quote Link to comment Share on other sites More sharing options...
Legacy777 Posted April 17, 2005 Share Posted April 17, 2005 the ECU is the MPFI unit. Quote Link to comment Share on other sites More sharing options...
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