Thermo fans always running diagnosis

[Gardna]

Hi all,

Have an issue with the thermo fans always running on my 3RB. Will come on with ingition and run constantly untill I turn off car, does this dead cold start air con off. Ran my OBDII yesterday watching temps and coolant is 65-70 degrees so fans shouldn't be on as from what I read the should kick in at 90 or so??

Could it be a faulty thermo switch, if so where is this located on the H6?

Anyone else experienced similar issues?

[Flat6Estate]

Is the air conditioning turned on or off when you're checking the fans?
If it is on, turn them off and check the fans again

[Gardna]

Air is off. Doesn't stop regardless. As soon as you turn ignition to on position fans run.

[Kekotic]

How long has this been happening?

[Brunsy3.0]

Faulty relay? Also interested in the outcome

[Gardna]

Noticed it last weekend so only about 5 days. Wasn't doing it before then. Better than the alternative of them not running

I'm thinking relay or switch, just need more info on where these are located etc.

[dr20t]

Do they cycle on and off constantly (as in two seconds on one second off continuously) ? Or are they just constantly spinning without cycling off at all?

If the former, it's in diagnostic or limp mode

If the latter, could be a number of things:

- fan relay in engine bay fuse box
- aircon compressor plug/ wiring earthing out

The fans run off a negative switch I believe, so also check the actual fan plugs for cracks / earthing out as this would keep them on

[Kekotic]

Do they cycle on and off constantly (as in two seconds on one second off continuously) ?

This was my initial thought that maybe it was in diagnostic mode.

[Gardna]

Both fans run all the time. No cycling.

Will have a look at relays after work.

[BillyCorgi]

You have been sent a PM containing a copy of the pdf for the 3.0L engine fans circuit.

According to the wiring diagram there is only power coming to the Radiator Fan Control Unit, Power from the Control Unit to the ECM, signal earth plus power out to the fans.

If the Fans are permanently ON then either the Radiator Fan Control Unit was had a whoopsey ( and thankfully failed ON) or the ECM is providing a false signal or there is a corruption in the wiring between Fan Control Unit and Engine Control Module.

If you have Select Monitor you could read what the fan status SHOULD be according to the ECM?

UPDATE:
Also just PM'd the diagnostic section from the H^ Engine section from the FSM.

[Gardna]

So I finally have an update. Sorry for the delay, had to put the car on hold for a while as moving and house renovations took priority of my time.

So the issue was the previous owner had butchered the wiring for the fans when doing a radiator change. He had not fitted the control module on the fan shroud when it was put back together. Wires were pushed into a plug connection and therefore had power all the time.

After a quote for the part from Subaru being a significant percentage of what I paid for the whole car, I got a fan with module attached from a wrecker at a 5th of the cost. Fans now cycle when required and issue sorted. Thanks for all the info