Hi I have a 55 reg Ford Fiesta 1.4 16v petrol and the car keeps over heating 

the temp gauge stays normal but engine gets very hot but the radiator cooling fan does not come on

i have tested the relay, coolant temp sensor, thermostat and connected a 12v battery to the fan terminals and the 30a fuse and all of these are working so not sure what else to check 

so any help would be much appreciated 

thanks 

 

If you have aircon, there are two relays that drive the fan.  One driven from the CTS via the ECU, and the other from air-con.  F4/FD is shown as a 40A

Thanks 

yes car does have aircon  the relay and fuse I checked was in car so is the other one in the black box near the battery

As far as I am aware, the only fuse for the fan is in the engine compartment fuse box - F4/FD 40A.

F12 10A, inside the car, is for the relay coils, not the supply to the fan motor.

Fast Fan relay is adjacent to the battery.  Does the fan start when you turn AC on ?

What resistance did you measure with the CTS ? and did it change if you warmed it up ?

hi thanks for your reply 
I replaced the coolant temp sensor and the thermostat but fan still doesn’t come on and no fan doesn’t come on when I put the air con on

On 4/15/2021 at 4:39 PM, Odd-job said:

Hi I have a 55 reg Ford Fiesta 1.4 16v petrol and the car keeps over heating 

the temp gauge stays normal but engine gets very hot but the radiator cooling fan does not come on

Hello Andrew, I have to ask the question - How do you know that your car is over heating if the Temp Gauge stays normal ?

Have you measured the temprature of the coolant by some other means ?

Because the coolant reservoir bubbles 

4 hours ago, Odd-job said:

Because the coolant reservoir bubbles 

The reservoir is the coolant expansion tank which is normally kept under pressure when the cap is screwed on tight. If I remember correctly the pressure relief cap opens at 21psi.

The operating temprature of the coolant when the engine is at temprature is about 90C but can get to 110C before you can consider the engine to be starting to over heat.

Put the top back on the expansion tank, close the bonnet and forget about the problem that  doesn't exsist.

 

23 hours ago, Odd-job said:

hi thanks for your reply 
I replaced the coolant temp sensor and the thermostat but fan still doesn’t come on and no fan doesn’t come on when I put the air con on

2 things to check.
The 40 amp fuse in the battery fusebox and the cooling fan resistor mounted close to the cooling fan.

The battery fusebox is sandwiched between the battery and the relay box, follow the short red wire from the battery.

I can vouch for the cooling fan resistor failing, mine did. The resistor coil is spot welded to the terminals, and 1 of the spot welds failed.

The fan should be running at low speed with the AC on!

Did you ever get this sorted.

Did you ever get this sorted.

On 4/22/2021 at 2:30 PM, unofix said:

The reservoir is the coolant expansion tank which is normally kept under pressure when the cap is screwed on tight. If I remember correctly the pressure relief cap opens at 21psi.

The operating temprature of the coolant when the engine is at temprature is about 90C but can get to 110C before you can consider the engine to be starting to over heat.

Put the top back on the expansion tank, close the bonnet and forget about the problem that  doesn't exsist.

 

That’s not really helpful. My son has same problem. Gauge stays normal but tank blows and fan not working

13 minutes ago, Petunafish said:

My son has same problem.

Then he should see a doctor!