CDTi Cooling Fan (again...)

[rob dean]

I know there are lots of threads on this theme, but I can't seem to find an situation exactly the same as mine:

The cooling fan on my 2004 (54 reg) CDTi runs continuously from when the ignition is turned on - irrespective of whether the air con is switched to 'auto' or 'econ'. It's shuts off about 10 seconds after switching off the engine. It's pretty noisy, but I'm unsure whether it's on high or low speed as I don't know what each should sound like.
Is this normal? Cause for concern?

Many thanks for any advice.

[T-Cut]

It might be worth checking the wiring to the coolant temperature sensor. If the connector/wiring fails, the system invokes emergency cooling whatever the situation A?C wise. If that seems OK I'd change the sensor itself.

TC

[rob dean]

Many thanks, will give that a try and let you know what happens.

[chrislloydie]

It might be worth checking the wiring to the coolant temperature sensor. If the connector/wiring fails, the system invokes emergency cooling whatever the situation A?C wise. If that seems OK I'd change the sensor itself.

TC


If so, would the coolant temperature IPK diagnostic check show the coolant as being higher than it actually is, thus tripping the high speed fan?

[rob dean]

Stupid question... Can anyone tell me where I can locate the coolant temperature sensor? It's all a bit croweded under the bonnet and I have no idea what I'm looking at!

[T-Cut]

On the diesel, it's located on the side of the head between two inlet ports (according to Mr Haynes - a recommended purchase for all DIYers).

TC

[bl52krz]

On the diesel, it's located on the side of the head between two inlet ports (according to Mr Haynes - a recommended purchase for all DIYers).

TC
could not agree more. bought my hanual before the car. always have done.

[JohnDotCom]

Still have a few Brand new sealed ones (Haynes) at £15.60 Post Paid.

[T-Cut]

If so, would the coolant temperature IPK diagnostic check show the coolant as being higher than it actually is, thus tripping the high speed fan?

Yes I think it would show something abnormal. If the sensor output isn't going to the ECU, it will have an effect on diagnostics. It's a good suggestion because people can check the output of the sensor using this method. An experiment is called for I guess.

TC

[Jules]

Hi Rob
If Temp sensor turns out to be OK, another possible cause is a "sticky" HIGH SPEED fan relay (buried deep behind slam panel)

Sensors schematic No 3 Temp sensor: http://www.the75andztclub.co.uk/forum/imagehosting/811477d92ca38ccd.bmp

Another process of elimination is to try this test: http://www.the75andztclub.co.uk/forum/showthread.php?t=35577

Switching the Trinary overide circuit in & out with the Aircon ON should toggle the fan between LOW & HIGH speed.;)

[andrewmsteve]

Hi does it switch off with the air con switched ie not on econ if so I think you may have lost a speed and it defaults to high speed I will try it on mine


Andrewmsteve

I have just tried it it should go off on econ so stickey relay maybe

[rob dean]

Hi Andrewmsteve

No, it's on all the time, irrespective of air con being switched, off, on econ or on auto.

I'm taking it to a local Rover specialist here in Wroclaw next week - the extent of my DIY abilities don't go far beyond washing it!

Thanks everyone for their suggestions, at least I know what to tell them at the garage if they need any clues!

Cheers
Rob

[rob dean]

In case anyone's interested, it turned out it was a blown relay. All sorted now, thanks to friendly local Rover garage. Now I can drive it without waking the neighbours (or the dead) with its howling cooling fan.:)

[Jules]

Glad it's sorted

The usual cause of burnt HIGH speed relay contacts is when the low speed fails either because of:

1. Worn brushes in a 3 speeder
2 Resistor failure in a 2 speeder

Either way, the 30 AMP contacts simply cannot take the 60 AMP surge to start the motor on full speed.
So anyone with missing speeds should get it seen to as it's a case of
Stitch in time saves nine!!