My 2006 3.0 Estate electric fan was running when I last drove on the 70 km trip that I do three times a week. I thought it would naturally run a second or ten and then turn off. I went to my appointment and an hour later a nurse came over and explained I had a very loud fan noise coming from the car. I ended up phoning the auto club (I was hooked up to a dialysis machine) and after having a look, they simply disconnected the battery. A few hours later I had a look at the engine bay and noted I was low on coolant but not enough to overheat the engine. I replaced the coolant and reconnected the battery. I also connected my OBDII reader and reset any flags - even though there were none noted. The fan still ran on. I looked at a few strings on this forum and noted one could pull a fuse. I found the 5A fuse in the engine bay which the manual showed was for the fan, but it failed to power it down. I suspect it might be the relay that has failed. I can hear a relay noise but no effect on the fan. I did read that I could check the voltage on the blue/white wires but am not certain exactly where those are found. I also read it might take a while for the fan to reset after refilling the coolant. I drove the 70 km home but the fan stayed on the whole time. The car is not running hot though. I certainly would like to be able to somehow pull the power lead for the fan though because I take the ferry with regularity and sit in lines a lot. Running my car for hours at a time while I sit, is very hard on my fuel bill and disconnecting the battery while in line is a pain in the *** because I need to reconnect while cars are moving around either in line or on the ferry. I have an appointment in town tomorrow and will go see my mechanic afterward but would rather resolve this today if I could. Does anyone know where the power leads for the fan are so I could unplug it for now?

 

Sorry to hear about this -how annoying. Have you tried simply disconnecting the fan controller module? It is located on the engine side of the radiator rail, towards the driver's side from the middle. There were two versions of this module, the early one being a finned rectangular box, and the later -which is probably the version in your car, a more rounded shape.
but do bring your coolant level up to the MAX line.

 

I see the module there and plugs on both sides but I am an old fellow with not much strength and couldn't get the plugs to release. Will see if the mechanic can manage it tomorrow. I may end up driving my XK8 if I can't resolve this immediately.

 

rigelprime, based on what you are saying, you have 1 of 2 issues going on here. The more likely problem is your fan controller has bitten the dust and you will need to have a new one fitted to the car. The "switches" inside the controller are known for failing after a lot of use and will fail by either not making the fan run or by making the fan run all the time. The less likely situation is your ECU failed and it is sending 12 VDC to the fan controller which is causing the fans to run all the time because it thinks the ECU is telling it the motor is too warm and to cool it off. This is where that blue/white wire running to the fan controller will tell you which issue you have.

You can try pulling fuse F16 in the engine bay fuse box. But, I think you are going to find that this fuse is not going to do much for you. This pretty much just tells the fan controller whether the car is on or off. The fuse you are more interested in is fuse F40 (80 amp, big fuse). Pulling this with the fan running is going to cause a nice arc, so, be ready. It will also spark nicely when you put the fuse in. Just keep your coat sleeve away. Not that I see it catching it on fire, but it would be a possibility, especially if you are wearing a coat that is very fuzzy on the sleeves.

If you need more help, let me know.

 

Hi @Rigelprime!

Your car has a fan assembly with two fans and one electronic control unit on it: Control Fan Module (CFM)
The CFM is more like a "power output stage" for two fan motors, (15A to 20A each at full speed?).

Like @Thermo described there are 2 possibilities:
- defective power output stage (CFM)
- defective control (wire or other electronic control units)

More likely are blown power semiconductors in the CFM (first possibility). You 've to replace the CFM.
But why are they blown!? Very likely because a previous error (which I think still exists) caused the fans to run continuosly.

So you have to change the CFM in the first step, then -when motor is in cold state- the fans shouldn't run at all (exept maybe when A/C is on).
If the fans are still running after CFM change (motor in cold state) you have to find the (second) cause!


The control is via the thin white/blue wire. The engine control unit controls the fan speed via a PWM signal. (When the wire is shorted to ground or shorted to +12V, the fans run on full speed, too.)
(If the wire is open, the fans should be off [healthy CFM is a prerequisite]. That's the way engine control module switches the fans off in normal operation.)

If the wire is really open (at or nearby the CFM), the engine control module should notice that and should set a DTC.
(Don't know of DTCs if control wire is shortened to ground or +12V. Or if the contact is unreliable.)


As an emergency solution you can unplug the supply plug of the CFM (left in travel direction). (It contains two thick power wires, and the thin white/blue control wire.)
(By the way: right in travel direction there are the two plugs for the two fan motors.)

The plugs have safety hooks. You have to release the hook to pull the plug!
The power supply plug (left in travel) is relatively easy to reach (in opposite to the both fan plugs).

You can drive without fans normally. But switch engine off if it goes to overheating!
In normal circumstances the fans doesn't run (except maybe when A/C is on) at all. Except it's very hot outside, and/or the engine runs in idle mode for a grater period.
I came to overheating when it's about +5°C outside and idling for 20 to 30 minutes (engine started from cold).


Cheers, catfondler

P.S.
If the fans ran a long period at full speed (high current, strong warming of the contacts, burn-off), their contacts in the plugs become unreliable. They have to be revised (when you change the CFM)!
It's important to do that for future reliable operation!

P.P.S.
Older models (before 2004/2005/2006?) have another CFM at the fan assembly (except the fan assembly has already been swapped to the newer one).