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[chrisr]

I know it's been warm lately but my rear radiator fan is running fast straight from a cold start, whereas it only used to kick in when the engine got hot, it switches off if I turn off the aircon. Any ideas?

[Doctor Gollum]

Stuck thermoswitch perhaps.

Do the front fans run?

[chrisr]

There's only one and yes it runs. Car is not overheating even with aircon turned off. Aircon working fine.

[Doctor Gollum]

Does the front fans run when the Aircon is on?

Basically the front fans(s) run with AC on and the rear fan runs when the thermoswitches tell it to.

When it gets properly hot it will run all the fans.

AC trumps the colder thermoswitch and the hotter one overrides everything.

[chrisr]

My car only has one front fan and one rear. I've just done a cold start with the aircon on auto, both fans started immediately. When I switched the aircon off both fans stopped. I presume the rear fan has two speeds as it was not as noisy as the other day, so I think things are working as normal and rear fan will switch to fast (noisier) speed when things warm up.

[chrisr]

I will be replacing the radiator later in the year, are the two switches on it the same? The car is a 2.2 petrol.
Thanks

[Doctor Gollum]

My car only has one front fan and one rear. I've just done a cold start with the aircon on auto, both fans started immediately. When I switched the aircon off both fans stopped. I presume the rear fan has two speeds as it was not as noisy as the other day, so I think things are working as normal and rear fan will switch to fast (noisier) speed when things warm up.

Certainly sounds like it, in which case, nothing to worry about from a fan perspective

[chrisr]

On further reflection, shouldn't the rear fan kick in and out from slow to fast speed as the radiator gets hotter and cooler? It seems that once it goes on to fast at the moment it stays there, I don't think this is right.

[Doctor Gollum]

That would depend on the radiator temps. The system is set up to run the fans as required as long as there's a charge in the battery. Hence the warning sticker on the slam panel

Think there's a guide in the FAQs and if you're any good with a wiring diagram, the one in Haynes will give a reasonable insight into which bit does what The MFL(later models) 2.0 16v and ECC should give you an idea

[TheBoy]

On further reflection, shouldn't the rear fan kick in and out from slow to fast speed as the radiator gets hotter and cooler? It seems that once it goes on to fast at the moment it stays there, I don't think this is right.

On the V6 - and 2.2 will be broadly similar, except less fans - the slow speed fan comes on at just over mid-point on the gauge (so around 96C on prefacelifts, and 87C on facelifts - the temps are actually the same if measured, but the gauge markings on the FL are lower for reasons only GM knows).

The high speed fan comes on as the needle approaches the upper marking on the gauge - so around 98/99C on PFL, and 88C on FL.  It's rare to hit these conditions except in hot weather after a run.


(All assuming A/C off, if on, obviously the slow fans come on anyway)


HTH