Technical Temp sensor.

[Rigby]

I'm 99.999999% sure that my temperature sensor is messing with the ECU. Fan pretty much always on, gauge goes to half way after half a mile and then sits pretty much constantly at 3/4 then goes up to the H and back down again. Changed the thermastat which made no difference, although nothing happened when I put the old one in boiling water. What are they like to change? Does anything else have to be removed?

 

[Neverth]

Engine?
On 2.0, 1.8 and 1.6 they/it can be found on the thermostat housing. Not that hard to change.
Separate circuit for dash and radiator. Might be in same sensor or separate (aircon or not?)
No aircon and radiator should have a thermostat switch that switches the fan on. Some with aircon also have this switch, on other the ECU controls the fan.
Not sure about 1.2 or 1.4 but shouldnt differ too much.
Sure the sensor has good ground as atleast the dash gauge uses bodyground on sensor.

 

[m20b25]

But you changed the thermostat...?

Start looking at the coolant temp switch/sender. Assuming a 1.2 CF2 takes a grey 3 pin type, CF3 takes a 4 pint black top. No more than £25 from Fiat

Very easy to change. I'll root out pics later when I can... Near the coil pack you should see it

 

[Rigby]

Dont worry about the pics, I've fixed it, hopefully! Gave the radiator a flush this morning and a thorough bleed untill the level didnt move at all and all seems well again, heater is working again too.

 

[bluejohn125]

Unless you've already refilled with expensive new antifreeze, it's probably worth adding some decent coolant system cleaner and running around with that to finally clean the gunge from your system, then doing a proper refill.

These cars do seem to need a good cooling system service every now and then.