Help Please, 99 OBW m/t Cooling Fan allways on ? with engine running.(even ice cold engine)

Things Ive done are : Tested and swaped around Relays under the hood, changed and tested before I installed new CTS, Good engine and body grounds. Tested Main Fan relay above fuse box inside car.

Fan will quit when Sub Control Relay is pulled. I fear ECU is going to lunch ? NO codes or CEL yet.

Dave in Upstate NY

One of the fans runs only when the air con is on. Verify what fan is running all the time. Go from there.

 

 

Jay

Main fan runs all the time,right side fan (engine running) other, left side fan will Cycle with A/C compressor or Defroster. Main was running this AM at start up 5 deg.

D.

Check your temp sensor, my 2.2 has one, I am assuming the 2.5 has one also.

the defrost function should kick the AC compressor on to dry out the air. So that *should* make the aux. fan turn on.

 

is the car having over cooling issues?

Thanks for replys, but NO_ONE is reading the First Post.

Fans are ALWAYS ON! Yes its having cooling Issues, Its to cool. main fan NEVER Turns Off. Anybody got any Ideas?

Its Not the relays, and its not the Coolant Temp Switch.

Dave

Could the Sub control relay have burned the contacts and latched itself?

 

Keep in mind that there are two coolant temp sensors, one for the dash dial, and one for the ECU.

I had the same problem in my 90 Leg, the fans came on as soon as I turned the key, I spent days (weeks) trying to find the problem, the temp sensor seemed like the most likely suspect a new one made no difference. I also changed the ECU and tore apart the entire harness looking for a bad wire. I never did find the problem.

Thanks for replys, but NO_ONE is reading the First Post.

 

I did

 

?

Its Not the relays, and its not the Coolant Temp Switch

 

This statement tells me you changed the fan thermo switch

 

The problem is the Fuel Injection Coolant Thermo Sensor.

 

Approx. 30 USD at the stealership

 

Located behind the engine block vent pipe for the PCV system.

 

 

Hope this helps, my EJ22 Legacy did the same thing.

Thanks for replys, but NO_ONE is reading the First Post.

 

I did

 

?

Its Not the relays, and its not the Coolant Temp Switch

 

This statement tells me you changed the fan thermo switch

 

The problem is the Fuel Injection Coolant Thermo Sensor.

 

Approx. 30 USD at the stealership

 

Located behind the engine block vent pipe for the PCV system.

Thats the switch I Changed, While I had the IACV off to clean it.

BTW: FI thermo sensor & Fan thermo switch are that very same switch on a EJ25 phase 1 engine.

Hope this helps, my EJ22 Legacy did the same thing.

I think I have it solved.I will post back with what I find:banghead: So that everone can benfit.

My legacy needs to have gas dumped on the air filter before it will start on cold days because of this problem. When the ECU gets a bad reading or no reading from the coolant temp sensor (CTS), it goes safe and turns on the fans. Better overcooled than overheated. Unfortunately, this seems to override the cold start-rich mix setup.

Did you find the problem? I had the same symptoms and never solved it.

No??? Ithought I was on the right track. I had a Subaru Tech. put Select Monitor on it, which showed FI temp sensor well in spec (it should new and replaced a week ago). But engine temp way too cool, He felt Lower hose it was cool to touch.

 

So I went after Water Pump and T/stat, (found rt side timing marks off 1 tooth, Car never idled & ran better now) Also I moved around relays, 2of them when put into Sub Fan Control would turn Kill always running Fan & other 2 would let fan run all the time. Well fan would cycle on after repair but never really cycle off.

 

As of last night, After car sat for 8hrs. Fan came on at start up, bottom hose Cold to luke Warm. BTW Tech Look for the infamous HG, NO obvious signs of that.

Problem fixed, Fuse for lighter was out, wich is also power for control side of one of the Main fan relays ??? WTF. Anyway ECM saw that M. fan circuit, inop & defaults to sub run low speed all the time to protect engine.

Once fuse was replaced :grin: . Everthings COOL.

Thanks for the info. I was just looking at a diagram and wondered why the ECU needed to be hooked into the circuit.