Hi there, I am experiencing an issue with my car’s temperature gauge. The car is a Ford fiesta flight 2001 with the endura-e 1.3 petrol engine. The temperature gauge does work but moves only a few millimetres onto the cold mark on the gauge. The fan never comes on even after a spirited drive. However In saying that, if I unplug the lead from the coolant temperature sensor the (assumed) fail safe cuts in and runs the fan even if the engine is cold so I know the fan has power. I replaced the coolant temperature sensor with no success.

There is no check engine light but I have scanned the car and received a p0115 fault code for ECT circuit fault. The plug to the ECT sensor receives around 4.6 Volts DC which I believe to be correct and another scanner shows on live data that the ECU/PCM is reading data from the ECT sensor.
I am a little stumped and frustrated and any ideas would be greatly appreciated. Thanks in advance and apologies for the information overload. 

Maybe a bit of a long shot (since I wouldn't expect this to cause a sensor failure code), but could it be the thermostat?  I don't know where it is on a 1.3, but you could check by starting the engine and grabbing the nearest thick hose you can see going to or from the radiator.  If it starts getting warm while the gauge still shows cool (instead of staying cold, then suddenly becoming hot as the thermostat opens), then I would look at the thermostat.

Thermostat stuck open, overcooling

I haven’t taken the thermostat out and tested it but it seems to be working as it should. When bleeding the coolant system after changing the ECT sensor,  the radiator and top hose were cold for around 5 minutes of running and then I could feel the rush of warm coolant as it opened. 
After a 3 mile journey and being parked up for a few minutes, the car was read on live data at 89 degree’s Celsius and the gauge still sat at the cold position so I don’t think over cooling is an issue but thanks for the responses. 

I don't think it's the ECT sensor, then, if you are getting reasonable live data.  If you are using ForScan, you can also get it to show the sensor voltage (I think it's called ECT_V).  If you were measuring it at the plug, then this would not take account for degraded wiring (corrosion, etc.) elsewhere.  Do you get the ECT code again after clearing it?

Also, if you use ForScan, see if it will do an instrument cluster test.  You never know.  On my similar vintage 1.4, you can get it to do an IC sweep test, although I can't remember how right now.  And in case these symptoms are not directly related (even though they do seem to be), try checking things like the fan relay.

2 hours ago, leederbyshire said:

I don't think it's the ECT sensor, then, if you are getting reasonable live data.  If you are using ForScan, you can also get it to show the sensor voltage (I think it's called ECT_V).  If you were measuring it at the plug, then this would not take account for degraded wiring (corrosion, etc.) elsewhere.  Do you get the ECT code again after clearing it?

Also, if you use ForScan, see if it will do an instrument cluster test.  You never know.  On my similar vintage 1.4, you can get it to do an IC sweep test, although I can't remember how right now.  And in case these symptoms are not directly related (even though they do seem to be), try checking things like the fan relay.

Not sure what make the reader was but it’s a decent model. If I get the opportunity again I will try and explore the different functions and try and get some more data out of it. The code was cleared but never checked for it coming back which maybe was a mistake, still, it made no change. 
when it was performing the scan it did do a cluster test and the gauge works. Another reason why I’m confused on the matter. Could possibly be bad wiring from ECU to gauge but I’m yet to rip the dash apart. 
That is a good point, I will look into checking the fan relay. I had the ECT sensor unplugged and was measuring resistance. It wasn’t the most accurate test as I could have just been making an on/off connection with the leads that go to the multimeter but when moving the wiring around, it did seem to have an intermittent resistance reading. Could this mean a break/short in the wiring? 

It could.  The car will have several separate harnesses, and the connectors between them could be worn, or oxidised, or full of water, or the cables frayed out of the back.  Try to get the probes secure with crocodile clips or something, and then try moving those wires around again, gently.  The sensor will not, of course be directly connected to the fan, or the dash; but it is simply an input to the ECU.  The fan and dash will have their own wiring, and (I'd guess) be on separate harnesses.  Although perhaps the fan is on the engine harness for convenience.

I shouldn't rip the dash apart just yet - you may upset the immobiliser or fry the ECU :-)

@leederbyshire Just an update on what I have discovered since I last posted. 
When the weather had warmed up a bit I had been driving and pulled over for a moment to make a phone call and the fan cut in. This made me think more so that the entire cooling system and ECU is working as it should and the issue is isolated to the gauge cluster/cluster wiring. 
 I recently found out that there is a sub-menu you can go into on the gauge cluster which allows you to perform a gauge test and also displays other information such as live temperature readings. The gauge test showed the temp gauge only reach a max of just past half-way (image below) which makes me wonder if you can physically move the gauge back to its true zero point which I have seen done or if it’s a wiring/voltage fault. The P0115 fault code would point to the latter. I think I will pull the cluster out this weekend and have a poke around and see if there is anything obvious wrong.

Hello again.  I've only just logged in again and seen your post.  The gauge test is also called a sweep test, so it ought to go to the full value when tested.  I guess the ECU is sending a range of voltages to move what are probably just voltmeters.  If you take the cluster off, I suppose you could supply your own progressively increasing voltages (1.5v battery, 5v from USB charger, 9v battery, 12v from car battery) directly to the gauge and see how it moves.  If it never reaches the max, then suspect a faulty gauge.  If it does, then suspect the wiring to it.  It's possible that rainwater is getting into the cluster, and affecting the readings.