Cooling Fans????

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newguy
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Cooling Fans????

Post by newguy »

Ok, I'm brand new to the site. I have recently purchased a 94 legacy 5spd front wheel drive. Great car, well built,, seems very easy to work on. The problem I'm having is the cooling fans won't come on.

Now, that being said the car never overheated while driving. The only reason I noticed was when changing the coolant, I was waiting for it to warm up and I noticed the fans were taking a long time to come on, I went around to the dash and noticed the temp gauge was higher then I had ever seen it.

Now, I know what your thinking, air in the system. I pain stack inly burped the cooling system to be sure. NO AIR. Now, while investigating some back yard wiring to the ac compressor I realized the fans work fine with the ac on (or defroster). As long as the ac compressor is turning both fans kick on.

Now, I've done the diag(plug in green plugs) and the ecm does NOT turn the fans on. The temp gauge is working great. The ect seems fine since if there was a problem with it the ecm should go into fail safe and make the fans stay on. After endless fuse checks the fuses all seem in order.

I haven't checked all relays properly due to a lack of the relay system diagram. I haven't located a good one yet and not sure which relays control what. The diagrams are missing on both box covers. I've located good ones for the fuses but no luck in being POSITIVE on the relays yet.

Any help/advice would be great. Why would the cooling fans not work off temp alone but work when the ac compressor tells them too?
wtdash
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Re: Cooling Fans????

Post by wtdash »

Welcome to the Forum,
Found this: http://bbs.legacycentral.org/viewtopic.php?f=19&t=47729

should help w/the relay(s), etc.

GL,
TD
Turbo Subies:
'87 GL-10 Turbo - SOLD
'90 BJ EJ22T/DOHC & 5speed swap - SOLD
'04 FXT, Forged internals, VF39, STI TMIC, Cobb AP- SOLD
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'96 BD-turbo'd-SOLD
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newguy
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Re: Cooling Fans????

Post by newguy »

Thanks for the reply, I was just getting on to update, I got bored(had the day off) and just went ahead and tested ALL the relays. They test out ok. I've heard of stories in the past that the relays are still bad even after testing.
But what's puzzling me is why don't the fans kick on in self diag mode with the green connector plugged in. Shouldn't ecm tell them to kick on regardless of weather or not the ect sensor says it hot enough when doing a self diag?
I hate electrical problems.
Also cleaned all the ground locations today. Didn't really seem like they needed it either.
wtdash
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Re: Cooling Fans????

Post by wtdash »

yes...the cooling fans should come on w/the GREEN connectors connected, AFAIK.
Td
Turbo Subies:
'87 GL-10 Turbo - SOLD
'90 BJ EJ22T/DOHC & 5speed swap - SOLD
'04 FXT, Forged internals, VF39, STI TMIC, Cobb AP- SOLD
'93 Legacy SS - 5-speed, SOLD :-(
'02 WRX -SOLD
'96 BD-turbo'd-SOLD
'98 SF - NA-T
newguy
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Re: Cooling Fans????

Post by newguy »

Another update, if anyone is reading this. Relays all test fine, jumper wire to fans=fans are working, new ect. I'm out of ideas.
Seems like the fans are not being told to turn on when they are suppose too. Also the ac trick doesn't work anymore either. Turn on the ac and defroster and nothing works anymore. Blows great heat though!!!
newguy
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Re: Cooling Fans????

Post by newguy »

Well, this is a very non active site.
mike-tracy
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Re: Cooling Fans????

Post by mike-tracy »

I think the service manuals in the "Stuff you need to know" section should have a diagnostic steps for troubleshooting this. If you've verified the fuses, relays and fans themselves are working, then the next step is to break out the multimeter and trace the wiring, unfortunately.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote: Mon Jan 14, 2002 10:23 am Wait....I'm confused now.
Legacy777
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Re: Cooling Fans????

Post by Legacy777 »

Welcome to the BBS.

I agree with Mike in that if the relays and fans all test good, then you need to check the wiring. The factory manual does have troubleshooting steps to walk you through what's going on. The other thing I would suggest is find the radiator fan output pin on the ECU and see if it's actually switching the fans on. If the ECU isn't switching the fans on, then there's a chance the engine coolant temp sensor is not working.

The fans along with all the other relays should cycle on and off with the green diagnostic connectors plugged in. Did you verify that the relays were cycling on and off? If the relays aren't cycling then your problem is between the relays and ECU or possibly the ECU itself.

However, you mention something about "backyard wiring". Can you elaborate what exactly you found? A large portion of problems are caused by previous owners "fixing" something.....they usually end up making things worse with their fix. I always recommend people try and put "modified" wiring back to stock so you can troubleshoot the actual problem vs. the symptom.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
newguy
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Re: Cooling Fans????

Post by newguy »

thanks for the reply, I have not tested the ecm, the coolant temp sensor is new. For 20 bucks I figured it wouldn't hurt to change it. The wireing I referred too was a hot wire run to the ac compressor. They had a toggle switch on the dash to force the compressor on, upon further investigation I found a burnt wire under the dash. Instead of locating a problem they just bypassed it. Now, both fans (at the same time) will come in as long as the ac compressor is working, but not for engine temp alone. Now, that being said, this car never over heats just driving normal, I've tested the temp gauge switch to be sure. The only way I can force a overheat is to rev it up too about 2500 and hold it while sitting still. Then the gauge will creep up but the fans won't kick on.
Legacy777
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Re: Cooling Fans????

Post by Legacy777 »

Yeah...it sounds like there is a problem somewhere with the wiring and/or ECU. It's possible that the radiator fan circuit in the ECU got fried due to a short or something. The AC sends a signal to the ECU to turn the fans on. I would check if that signal is present and working, and then I would check if the ECU is sending a signal to switch the fans on when the AC is turned on (without using the manual switch).

Are you able to trace the wire to a particular connector or junction?

Check out the Stuff You Need to Know forum to d/l service manuals
http://bbs.legacycentral.org/viewtopic.php?f=12&t=14485

Also, these ECU I/O lists should helpful

http://www.surrealmirage.com/vrg3/ecupins/

The Excel file is for a turbo Legacy. Some of the pins are different, but the spreadsheet gives a little more info on some pins than the website.
http://main.experiencetherave.com/subar ... CU_I-O.xls
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
newguy
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Re: Cooling Fans????

Post by newguy »

Well guys, its been months and I haven't been on here. Due to the winter time weather I haven't messed with the car, as I stated it never overheats when driving normal. But... warmer weather is coming and I am sure now is the time to fix my cooling fans, before I have a problem down the road. Here's where I am at. Basically the same as all above. Cooling fans won't operate or cycle on there own. If you kick the defroster on or the a/c then both fans will kick on briefly. (ac system is cycling properly but I think that is a unrelated problem) Now the back yard wiring mentioned way earlier was a hot wire ran directly to the a/c compressor with a toggle switch on the dash to force the compressor on(related to the a/c system not cycling properly I'm sure) and I have removed all of that and put things back to stock. I have ran jumper wires to the fans themselves and they will run all day when hot wired. I have check ALL relays and fuses and everything checks out. Now, in the last couple weeks my cruise has quit working for no apparent reason either. Fuses/relays all test good. Here's where I'm at, I don't have the means or time to properly check ecm pins. Does everyone(if anyone is reading) agree at this point there is more then likely a computer problem? I have traced wire after wire all over this car and the old girl is in really good shape. No corroded or broken wires I have come across anywhere. Please give opinions.
Legacy777
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Re: Cooling Fans????

Post by Legacy777 »

The ECU's don't typically go bad without something else causing them to go bad (electrical short or similar). The engine ECU is different than the cruise ECU. Without doing some more diagnostic I couldn't say that the two are related with 100% confidence.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
newguy
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Re: Cooling Fans????

Post by newguy »

alright fellas, I bit the bullet and took to a garage, they said it's the ecm. (which I think they mean the ecu). I picked the car back up and am on the hunt for one. Does anyone know the best place to get one, new or used, and what info do they need? Where is it located? Any help would be greatly appreciated.
Legacy777
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Re: Cooling Fans????

Post by Legacy777 »

Definitely get a used one. Any 92-94 non-turbo Legacy ECU should work. I'd try posting something in the parts shed forum and check out any local junk yards. What part of the country do you live in?


What did the shop do to verify it was the ECU that is bad? I still maintain the fact the ECU's typically don't go bad on their own and if they are bad it's usually caused by a short and there are other drivability issues.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
newguy
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Re: Cooling Fans????

Post by newguy »

well, with all the different opinions I decided to remove the ecu and send it off to be tested. It cost 90 bucks for diag or 225 for repair but I figure its worth it. We'll see. Be a few days before I know anything.
rallyak
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Re: Cooling Fans????

Post by rallyak »

Buying a use one would be cheaper.
Charles

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