[karlaudi]

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

 

[karlaudi]

Thermofan switches are most often located in the bottom tank of the radiator close to the lower hose. Or the lower radiator hose on side tank radiators. They are what turns electric radiator cooling fans on according to coolant temperature in the radiator. Check your thermostat too if no hot coolant reaches the radiator so that the fans turn on.

You may wish to see if a Subaru Service Manual is available from Subaru for your model and year. The price is right for downloading a PDF manual plus other information.

The link:


https://techinfo.subaru.com/stis/#/login

 

[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

 

[karlaudi]

The Factory manual for my 2010 says the thermostat begins to open between 176- 183 degrees Fahrenheit and is fully open at 203 degrees Fahrenheit.

Thermostats are suppose to fail in the open position, but not always. I have experienced at least one that failed closed and this sounds like thermostat has failed closed. But is the water pump even working? Why was the radiator replaced?