Engine cooling fans

[Rogerwilliams]

The radiator fans on my 3.2 x300 are permanently running when the ignition is switched on. Is this normal?

[naki]

No. Your fan relay has likely gone open circuit.(its white and located under the front bumper, behind the LH corner.)
I have spares here if needed.
It could also be the thermal switch in the rad, but those are more reliable generally.

[cafcpete]

The answer is Yes or No! It all depends on if you have the shorting plug modification or not.

There was a TSB that changed the operation of the fans after reports of the fuses blowing, so the operation was changed to always ON low.

https://www.jaguarforums.com/forum/atta ... ailure.pdf

Peter

[steve_m]

Mine is coming on now as soon as the key is turned i.e. before the ignition comes on.
I have a replacement rad switch and relay but how the hell do you get to the relay?
Is it a bumper off job?

[cafcpete]

There meant to come on Steve if you have the jumper wire (see TSB).

[steve_m]

It never used to and it doesn't have a jumper wire.
I just need to know how to access the relay; I've seen photos of the location but don't know how to get to it.

[cafcpete]

If I was to guess it’s got at by removing the front underskirt. If that fails then bumper off but start with the skirt!

[steve_m]

Got my mechanic to do it which is even easier.
Anyway, the stupid fan started behaving itself today for some reason.

[cafcpete]

Glad you have it sorted for now, but If it was me, I would fit the shorting wire as per the TSB, just to avoid a problem happening in future. It is a pain the fans running all the time, but better that then them not running at all when you need them!

[steve_m]

Now it is back to running all the time even though the relay was changed.
Had a wizard idea and pulled the plug on the thermal switch and connected it to the new switch; no difference even with a ground wire on the sensor side of it.
I still don't quite understand why they would come on before the ignition is on i.e. the first position of the key.

[Rogerwilliams]

Surely if both fans are running at full speed from cold it will stop the engine reaching normal running temperature which will have a dramatic effect on fuel consumption

[cafcpete]

It’s not at full speed, but low speed.
It will mean that warmup is slower, but Jaguar decided this was a price worth paying to stop the fuses blowing when there was was a high demand start up current.
The fuse is to protect the cable, so they couldn’t just raise the fuse rating without changing the loom. My guess is that someone at Ford was cutting cost (and weight) and under spected the fan cables.
So much easier (and cheaper) to put a shorting wire in the circuit than have a recall and pull the whole car apart to change a major wiring loom!

[Rogerwilliams]

I understand what you say but I can travel 15 miles and the temperature gauge barely moves. I realise that the cold weather doesn’t help but it can’t do the bigness any good running so cold

[cafcpete]

That way to long, they should have moved in that time.
Check your thermostat first.
Also I believe there are TWO temperature sensors on our cars. One tells the ecu what the temperature is (for fuelling etc) and one to operate the gauge. So you may have a faulty sender. It’s worth getting a cheap odb2 real time reader as this will tell you what the car thinks the temperature is.

You could always pull the two fan fuses before you go for a drive for cold and see if that makes a difference but remember to put them back one up to temperature!

[steve_m]

Really blurry when zoomed out; is that 11 and 30 for the fans?