[2.5x_sleeper]

The earlier ECM are pretty basic... no serious magic. As long as the ECM is off a like Forester, you should be good.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[Derek'sForester]

Thanks. I guess I'll know by this Friday if I've exhausted my efforts.

 

[Derek'sForester]

Well I just installed a used ECM and no results whatsoever. Is there anything else that this could possibly be? I've checked every fuse and have switched relays and nothing changes. Some people havre referred to two coolant temperature sensors, I can only find one. I've even got a new radiator cap. Has anyone else had this particular problem?

 

[Kevin]

Did you check the radiator thermofan switch(es)? on the radiator?

I'm putting it up on ramps today and I'll try to locate the sensors that were referred to in an earlier post.

The sensors referred to by karlaudi did not exist on either of my Subarus therefore I doubt very much they would be on your vehicle. The workshop manual for MY'03 (incls non-turbo and turbo) refers to just one "Engine Coolant Sensor". As well there is the "Intake Air Temp Sensor" and the "ATF Temp Sensor" but I cannot imagine either of these stopping the fans.

If the car needs to be used just run direct fused power to the fans with a switch under the hood. I did this as a temporary fix in the past.

 

[2.5x_sleeper]

@Derek'sForester questions:

[1] Just to verify... when you connected the green test connector, did the both radiator cooling fans operate?
[2] Have you read the coolant temperature with a scan tool, Scangauge II or an UltraGauge?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[Kevin]

Yes, they did both come on Bobby.

I did the diagnostic test and the fans function.

It would be interesting to see if any old codes exist.

 

[2.5x_sleeper]

I just wanted to be 100% sure.

Curious that the radiator fans don't operate when the A/C is activated?

The wiring diagram shows the radiator fan relays are controlled by the ECM, which applies a ground (-12V) to the relays to operate one or both.

The coolant temperature sensor & A/C system connect to the ECM, which controls the radiator fan relays. Neither directly connect radiator fan relays.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

Yes. I replaced it last Sunday. It was the one in the back of the engine under the intake manifold. It had a three prong connector. It didn't seem to make any difference. <snipped>

You said the coolant temperature sensor had "3 prongs". Did that sensor have 3 wires or 2 wires?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[Derek'sForester]

It's really hard to see, but as far as I can tell there are two, a green one and a white one. I'd have to disassemble the ducts leading to the throttle body again to get a better look.

 

[Derek'sForester]

Yes, they did both come on Bobby.

It would be interesting to see if any old codes exist.

The only code was 'fan malfunction'. I forget the number. I should have written it down. I kind of remember it was 1408, or something close. I just put my scanner on it and it read no codes. Even though it has been started and got hot, but not to the red mark.

 

[Derek'sForester]

@Derek'sForester questions:

[1] Just to verify... when you connected the green test connector, did the both radiator cooling fans operate?
[2] Have you read the coolant temperature with a scan tool, Scangauge II or an UltraGauge?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

I don't believe that I have a scanner that can perform that function. I'll probably need to buy one. I have a Schwaben by Foxwell. It is set up to read OBDII, as well as BMWs.

 

[karlaudi]

The sensors referred to by karlaudi did not exist on either of my Subarus therefore I doubt very much they would be on your vehicle. The workshop manual for MY'03 (incls non-turbo and turbo) refers to just one "Engine Coolant Sensor". As well there is the "Intake Air Temp Sensor" and the "ATF Temp Sensor" but I cannot imagine either of these stopping the fans.

If the car needs to be used just run direct fused power to the fans with a switch under the hood. I did this as a temporary fix in the past.

I stand corrected, Kevin. Except for my very first car when I was in the Navy, and then only for a few months before I bought a VW (it was a 1964 6-cyl 2 dr. Chevy Bel Air), VWs and Audis are all I have owned since 1976. My first water-cooled VW was in 1981 and I was also working in a shop at the time that focused only on German Cars and then mostly VW and Audi automobiles. I have seen a lot of thermofan switches in my day.

The 2010 Forester, I now have to give to my oldest daughter, is the first non German/ European car I have had any in depth experience with outside of my college training and what European relatives own.

So I assumed. Oops!

I was a bit surprised after reading your comment and then checking my Subaru Service Manual that, in point of fact, there was no thermofan switch(s) in the radiator. The Subaru is the first design I have seen close up (or owned), and there maybe others, where the cooling fans and their replays, are controlled in operation through the engine ECU.


Thank You Again

 

[2.5x_sleeper]

It's really hard to see, but as far as I can tell there are two, a green one and a white one. I'd have to disassemble the ducts leading to the throttle body again to get a better look.

The wiring diagram shows a 2 wire coolant temperature sensor, so your "3 prong" description threw me.

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

This is a VERY curious problem!

The radiator fans operate when the test connector is connected, so that proves the radiator fans can be controlled by the ECM... pins [a3] main fan [a12] sub fan.

The coolant temperature sensor connects to the ECM, pins [c14] - Does the ECM see this sensor... the coolant temperature? This needs to be verified with device attached to the OBD2 connector.

The A/C system connects to the ECM, pins [b27] [a17] [c30] - Does the A/C work... was it working?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[Derek'sForester]

The A/C doesn't work. My son said it did in the past. We haven't needed it for months, until this week.

 

[Derek'sForester]

So I figured out how to check the engine cooling temperature. It stayed at about 160 as the temp gauge headed towards the red. I turned off the engine before it hit the red mark. The coolant temp stayed at 160. When I earlier removed the coolant temperature sensor very little coolant came out. Does this mean I have air in the system? Do I need to re-bleed it? Could this be a thermostat issue which is not letting the coolant circulate? However the heater is putting out hot air. I bought a coolant funnel thing that will arrive on Monday. I never had issues like this with my SVXs.
Any ideas?

 

[Kevin]

Could be a thermostat issue. If you run the engine with the radiator cap off is there any evidence of flow and/or the coolant getting hot?

I'm pretty sure the heater connection is independent of the thermostat so it can get heat without coolant flowing through the thermostat.

 

[Derek'sForester]

@Kevin We had a very cold winter, for Oregon that is. Maybe that's what started this out. If I pull the radiator cap the coolant drops and feels hot. Since we got this car right before winter set in it's hard to tell what it will do in hot weather. We did have to put in a new radiator right after we got it. It was a free car from an old friend that had sat for awhile. Maybe the cold winter hid the issue until spring, but my son says he heard the fans before. He's never been much of a car guy. Maybe I'll drain the system because that's what you have to do to access the thermostat.
It appears to be grasping at straws time. I always thought that if the heater worked that meant the cooling system was circulating the coolant well. Maybe I ws wrong.
At least it's not an Audi A4. You had to pull the front of the whole engine apart to to change the thermostat in those, at least the 2.7 V6.

 

[2.5x_sleeper]

Curious... if the coolant temperature is 160F, then that's too cool for the radiator fans to operate. In addition, at 160F how can the coolant gauge be showing hot, in the red?

Normal coolant temp is 190F to a touch over 200F.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[Kevin]

I always thought that if the heater worked that meant the cooling system was circulating the coolant well.

There is a heater bypass hose from the water pump so the heater can function without coolant flowing through the thermostat.