Hi everyone, first post on here, been a long time since being on a forum. 

We have an issue with our 2005 Fiesta 1.4 Zetec radiator, I see other posts from years gone by on here have asked similar things, but none seem to get to a conclusion. 

The issue - the radiator fan doesn't come on, even after the car was clearly overheating after a long journey and sitting idling for sometime at the end with steam billowing out the expansion cap. 

I have replaced the engine water temp sensor (I understand this acts as the switch for the radiator), the water tank and expansion tank (cap is meant to release pressure so I believe) and the tank had a split in it. Checked the fuses and they're all good, tested relays by swapping them over with other ones in the car to test. I have removed the plug to the water temp sensor and the fan switches on, so the fan does work and the wiring must be fine. 

The only thing I don't understand is people say the fan should come on when the AC is switched on, this cars AC hasn't works for years, and the fan doesn't come on when the AC switch is pressed (still lights up / powered etc).  

Can anyone think of any other reason why the fan does not come on, short of running a home made bodge switch to override it, I'm all out of ideas. 

Thanks 

The fan only comes on with AC if the compressor kicks in.  If the compressor doesn't kick in because the AC gas pressure is too low, the fan won't come on either.

If you have a look at the bottom corner of your fan shroud, is there a triangular plug with a small green cylinder on it?  That's the fan resistor, and is what stopped the fan working on a 1.4 Mk6 that I had briefly.  The resistor isn't fitted to many Mk6s though, and I never really did confirm which ones, so it's easiest just to have a look rather than try to guess!

Looks something like this - 

Thanks Tom, just gone and checked, doesn't look like ours has one of those resistors. 

The thing that confuses me is the fan works when the water temp sensor is unplugged, putting the car into a 'safe mode' as it doesn't know the temperature. So electrically, surely everything works and is okay as the fan operates? It may be an old car but I've even used genuine parts such as the new temp sensor as I try to rule out poor quality parts adding a problem. Sensor seems to work okay. 

 

 

The fan runs at full speed when you unplug the sensor.  It should run at slow speed when the coolant temp starts creeping up, that's the function that I think is missing here.

They don't start running at high speed on these until well over 100c, (possibly 107c from the top of my head), which is useless when there's a leak because it'll boil the coolant off and there'll be steam billowing out long before then.  The system is pressurised when sealed to raise the boiling point. 

So it could still be a faulty relay or wiring for the half speed function.  All we can say for sure at the moment is that the fan motor works fine.  With that in mind, your suggestion of an additional fan switch is probably the quickest solution.

Have you checked/replaced relay 2 in the engine bay ?

It is listed as 'High Speed' Fan, but as far as I know actually switches the fan between slow speed and high speed.

Also, I'd expect that that there must still be a dropped resister 'somewhere' even if it is not mounted on the radiator cowling like the one in the picture. To run the fan at any speed other that full, would require a means to reduce the voltage to the fan motor. The quickest, easiest, cheapest would be to use a resistor so I expect that there will be one, you just have to find it.

Looks like the resistor is only fitted to models with AC.

 

I think the OP has given up !

Last visited the forum 11th July after making two posts.

5 hours ago, unofix said:

I think the OP has given up !

Last visited the forum 11th July after making two posts.

Well…. We can only do what we can. 

On 7/10/2023 at 1:23 PM, tez162003 said:

Hi everyone, first post on here, been a long time since being on a forum. 

We have an issue with our 2005 Fiesta 1.4 Zetec radiator, I see other posts from years gone by on here have asked similar things, but none seem to get to a conclusion. 

The issue - the radiator fan doesn't come on, even after the car was clearly overheating after a long journey and sitting idling for sometime at the end with steam billowing out the expansion cap. 

I have replaced the engine water temp sensor (I understand this acts as the switch for the radiator), the water tank and expansion tank (cap is meant to release pressure so I believe) and the tank had a split in it. Checked the fuses and they're all good, tested relays by swapping them over with other ones in the car to test. I have removed the plug to the water temp sensor and the fan switches on, so the fan does work and the wiring must be fine. 

The only thing I don't understand is people say the fan should come on when the AC is switched on, this cars AC hasn't works for years, and the fan doesn't come on when the AC switch is pressed (still lights up / powered etc).  

Can anyone think of any other reason why the fan does not come on, short of running a home made bodge switch to override it, I'm all out of ideas. 

Thanks 

unless you have a blockage in the water jacket and hot water is not reaching the sensor sounds like you have checked most things, have you checked the mechanical thermostat ???? 

can l add to this post that l am having exactly the same issues as described,l have also noticed that the temp gauge is reading around 80c when the coolant is actually boiling, the picture shown with the relays in the box is different on mine as there is only one relay in this location,l suspect that it will probably be the resistor as mentioned but l have searched everywhere and cannot locate it.tia

3 minutes ago, 1higgins said:

can l add to this post that l am having exactly the same issues as described,l have also noticed that the temp gauge is reading around 80c when the coolant is actually boiling, the picture shown with the relays in the box is different on mine as there is only one relay in this location,l suspect that it will probably be the resistor as mentioned but l have searched everywhere and cannot locate it.tia

The fan won't come on if the temp is only reading 80c.

If the coolant in the reservoir is boiling when the gauge reads 80c, it is more likely to be a faulty cap or a cracked reservoir preventing the coolant from pressurising.