Radiator fans not coming on properly
 

Hi everyone.

My 2006 Impreza started overheating and when I stopped I noticed 2 things; the header tank had ejected a lot of it's contents and the radiator fans didn't come on. They both turn on if the A/C is turned on. The dash fault indicator doesn't come on.

I checked all fuses and the fan relays which are fine. There is a voltage on one pin of the coil of the main fan relay, but the other side of the relay coil never gets grounded, even when the temp is 99C and the car is stationery. If I ground that side of the coil the relay turns on and the fan runs. After a while the dash fault indicator comes on.

From the wiring diagram I see that the relay is turned on by the ECM grounding that side of the relay which it's not doing. Does this mean that the ECM is faulty :eek: or could it be something else (hopefully!)?

Appreciate any input.

***Updated due to not being RHD turbo model but a LHD 1.6L SOHC model
Wiring for European MY06/07 Impreza non turbo models attached.
Yes the ECU grounds the relay coils to operate the fans but if both work when the A/C is turned on the ECU is doing its thing.
I would check/replace that both the "Coolant temp sensor/thermometer" circuits are working.

Pins 1&2 - ECU temp circuit
PIn 3 - Dash gauge
https://cimg5.ibsrv.net/gimg/www.sco...e693a0a601.jpg

One side of the dash gauge is earthed via the sensor body hence the copper washer - no thread tape

https://cimg2.ibsrv.net/gimg/www.sco...7731eda376.jpg

Thanks Don.

The temp coolant sensor was replaced very recently when it failed. When I monitor the temp using my ODBC reader as the car warms up and the thermostat opens, the temps seem to be totally normal. Also, I've checked the top/bottom hose temps using an IT thermometer and it confirms what my reader is showing.

I'll check the wiring from the fuse box back to the ECU - maybe there's an issue.

How do I find the connector F45/B62?
Thanks!
https://cimg6.ibsrv.net/gimg/www.sco...bde3240342.jpg

First off you won't as you are looking at a LHD drawing, probably the US version.

Correct European LHD SOHC version
https://cimg7.ibsrv.net/gimg/www.sco...46e882ca64.jpg
Front Loom diag
https://cimg9.ibsrv.net/gimg/www.sco...c5f9bc5c0d.jpg
https://cimg2.ibsrv.net/gimg/www.sco...f3c385cb59.jpg


Bulkhead in compartment
https://cimg1.ibsrv.net/gimg/www.sco...e278469906.jpg
https://cimg7.ibsrv.net/gimg/www.sco...9019d95bbf.jpg

Hi Don,
Thanks for that. Sorry that I didn't spell it out at the top of my post. Mine is a LHD, 2006, non-turbo Impreza with SOHC. Engine EJ16.
Maybe it's easiest if I just check continuity from the fusebox to the ECU, and also the voltage at the relevant pin on the ECU?

Cheers.

OK

LHD Front loom F45 in cabin to the left of steering coumn

https://cimg1.ibsrv.net/gimg/www.sco...f2c3005542.jpg
Bulkhead loom in compartment/cabin

https://cimg0.ibsrv.net/gimg/www.sco...8935e724b1.jpg

Many thanks, Don. I'll start finding those bits.

I've pulled the ECU and it doesn't match any of the diagrams I see in my workshop manual. There are 4 connectors, each with 3 rows of pins. How do I know which is the main fan control pin?
Thanks!
https://cimg8.ibsrv.net/gimg/www.sco...5494135b68.jpg

What's the part number of the ECU?

OK.
Have attached both correct Fan diagram and ECU pinout for the H4SO engines as pdf's
And have updated previous replies due to in correct model info.
ECU as far as I can tell should be a 22611AL230 ??

https://cimg2.ibsrv.net/gimg/www.sco...16f8d57693.jpg

https://cimg6.ibsrv.net/gimg/www.sco...5e13b4698e.jpg



In the European manuals only the main engine outputs are listed for the ECUpinouts
The fan control pin numbers will need to be confirmed from the fan wiring diagram for wire colour and pin location.

Yes, you're correct, that's the exact ECM.

Just to confirm that I'm testing the correct pins:
Fan 1 is pin #14 on B134 the connector furthest left, and counting pins in the middle row starting at #9 from the right (ECM pinout diagram) looking into the back of the ECM. From the Non Turbo Fans diagram it starts #9 from the left!
Fan 2 is pin #13.

Are these 2 wires coloured RL and GW (whatever those colours are)? Not sure it helps me much as I'm partially colour blind so I might have to ask for help.

Many thanks.

One diagram shows the face of the ECU the other the face of the connecting plug
distinguished by the solid black and clear rectangles. You will have to confirm which is which in this inst with the wire colours.

ECM diagram
https://cimg7.ibsrv.net/gimg/www.sco...42c0f9471b.jpg

Fan diagram
https://cimg5.ibsrv.net/gimg/www.sco...314fcb551a.jpg


Colours: RL is Red/bLue stripe; GR is Green/White stripe

https://cimg4.ibsrv.net/gimg/www.sco...3551445f88.png

OK, I've found the main fan pin. What do I need to check for when cold and hot? A voltage relative to somewhere or a resistance between some points?

Thanks.

When the ECU/ECM receives the required voltage signal from the Engine coolant temp sensor the ECU will ground pin A14 and turn on the fan
Engine coolant temp sensor sends signal to B135 pin12 - as per ECM pinout.
https://cimg4.ibsrv.net/gimg/www.sco...007594cf8a.jpg

When the A/C control unit sends the "on" signal to the ECU (either B137 pin D13 or B136 pin C11) the ECU grounds both fans via pins A14 and A13
https://cimg1.ibsrv.net/gimg/www.sco...2489a502e8.jpg

AS you said in your original post "They both turn on if the A/C is turned on." i believe the problem lies in the coolant temp side of things.
For the non turbo models the Coolant temp gauge is a separate circuit from the ECU signal although part of the same sensor.
Either the ECU is not receiving the signal from the sensor (B135 pin12) or the ECU's circuitry for this input is not grounding A14.
Make sure B135 pin19 is grounded
In fact probably make sure all the engine grounds are good and clean.
https://cimg5.ibsrv.net/gimg/www.sco...0fd5227ca8.jpg
https://cimg4.ibsrv.net/gimg/www.sco...bb6dd9a861.jpg

Thanks very much for that. Need to spend some time in the car with the multimeter now!

In test mode (green plugs under dash): Both fans cycle normally.

Now, when I turn on the aircon, only sub fan runs.

Tested with ignition on/engine off:
Voltage on pin #14 for main fan = 12V
Voltage on pin #13 for sub-fan = 0.12V

Tested with ignition on/engine on (cold and hot):
Voltage on pin #14 for main fan = 12V

I ran a wire from the relay coil directly back to Pin #14 on the ECU (to rule out a wiring problem) but there's no change.

Checked the OBD temp reading with an IR thermometer. Thermostat opens about 87deg.

Looks like it's the ECU after all :wall:

With both fans hard-wired on she runs about 105/106deg without even going uphill, but I think that's just another problem!

Don - I really appreciate all the invaluable help.