Engine temperature gauge malfunction?

[AdrianY]

Posted in BMax forum but copied here as BMax is a derivative of Fiesta

I have a top-of-the-range 2016 BMax.

My engine temperature gauge rarely indicates any temperature. It looks like the normal range should be between two and four bars. But except on the hottest summer days, the gauge never budges from zero.  The Fire dealer tested it and found no DTCS present (I think that means a diagnostic testing code). They then turned off the AC and found, using a cataloguer, the the figures increase OK. They went on to say the car will take longer to warm up when AC is on due to the fan constantly running for AC.

But I find that with and without the AC running makes very little difference.

This winter I have found the cabin temperature take a very long time to warm up and it never really gets 'warm' as you'd expect when the cabin temperature is set too high.

A friend has a Fiesta, but with a lower spec AC system. He says his temp gauge is always between two and four bars.

Quite a puzzle. Any ideas?

[Aldridge Andy]

Sounds like a coolant thermostat is stuck open 

[DaveT70]

10 hours ago, Aldridge Andy said:

Sounds like a coolant thermostat is stuck open 

Absolutely. Over cooling, change the thermostat

[Cragrat]

ecoboost 1.0 has two thermostats. One at the top easy to replace the other at the bottom and is a right pain.

 

[DaveT70]

1 minute ago, Cragrat said:

ecoboost 1.0 has two thermostats. One at the top easy to replace the other at the bottom and is a right pain.

 

Didn't know that, thanks. Every day's a school day

[Tdci-Peter]

11 hours ago, AdrianY said:

They went on to say the car will take longer to warm up when AC is on due to the fan constantly running for AC.

They are talking rubbish! Yes, the fan always runs while the AC is on, but if the thermostat is properly closed it makes no difference how fast the fan runs, as almost no heat should be getting to the radiator.

So if the engine heats up while stationary, with a/c off, then that points to thermostat. It should be easy to test if the radiator & its hoses are warming up straight after a cold start.