2015 1.6 non turbo overheating

[Will1987]

Hi guys my temp gauge is not working properly. It always either reads nothing on cold start, witch I would say that's normal but after about 15min of driving it automatically jumps to normal range. With no gradual climb. Or after it's been cooling for say 3 to 4 hours and you start the vehicle it automatically is in nornal operating range. No gradual climb from 0 bars. Also my cooling fan is not coming on at all with temp only when a/c is on. So naturally I figured a faulty temp sensor. Changed temp sensor semptoms still the same. My scan tool tells me the ecm is reading temp. But my car will overheat before the instrument panle or cooling fan does anything. I have looked all over for another temp sensor in the system but can't seem to find anything about this vehicle having a CHT sensor. Can any one help with this or do I need to take to dealer.

 

[econoboxrocks]

How old is your battery?
If it's old, it may have enough juice to start the car, but not to run all the electrics. Fiestas are very picky about voltage flow. An old, but not worn out battery can cause issues like you describe.

 

[scotman]

The OP doesn't mention how many miles are on his Fiesta. So, i would be checking the ect sensor and the cooling fan relay as well as the ground connections that reside under the battery tray.
If the Fiesta has more than 60 thousand miles, i would be looking at the water pump as well as the condition of the coolant. If the coolant is either old or has been boiled out and then topped up, i would be getting the entire system power flushed.
If the coolant reservoir has been requiring frequent top ups of coolant level prior to the overheating events, i would be replacing the reservoir as well. I have "trust issues" with that damn component.

 

[Will1987]

How old is your battery?
If it's old, it may have enough juice to start the car, but not to run all the electrics. Fiestas are very picky about voltage flow. An old, but not worn out battery can cause issues like you describe.

Thank you. Batt is weak but does start the car.

 

[scotman]

You need to get rid of that weak battery ASAP! That situation is the cause of so many odd behaviors because a failing battery places much greater demand on the alternator to keep up with operating the various equipment on the car. Most people have no idea how much draw on the electrical system is created by leaving the radio and the air-conditioning switched on!
People give no thought to it. The car generally has enough reserve capacity to crank and start with an additional load. But expecting a weak one to do that trick many times without voltage drops or spikes is unrealistic. Thanks to the Canbus electrical systems in the modern car, very small but precise power levels are a required condition for the many controllers, relays and switches that are in constant communication with each other and the main processor.