I have a 2018 pre face-lift focus,the engine temperature never goes above about 65-67 celcius when air con is on and in auto mode, but rises to around 90 when switching them off,is this normal? The eco mode always reads 100% journeys are below normal temperatures or words to that effect

2 hours ago, almo5060 said:

I have a 2018 pre face-lift focus

That's a bit of a confusing statement.

You either have a Focus Mk3.5 also known as a Mk3 facelift, OR, you have a Focus Mk4.

Must be mk 3.5 then ,it's the one with the wet belt not the chain

 

The thermostat is weak.

Using AC causes the fan to run and the grille shutters to open, so a lot more cooling air over the radiator with the AC on.

the hotter the engine the more efficient it gets - she has a 57 plate 1.6vvti focus "zetec climate" it came with fast clear door mirrors, and a front heated screen - and the mirrors and both front and rear screens come on automatically if its below 3C... plus its got the variable rate AC compressor

and the point of the post - this mad one, got an electrically heated engine cooling thermostat - its designed to run slightly hot for increased efficiency - then if you floor the throttle, find a big hill and the AC is working hard - the heated stat cuts in to rapidly open up the main cooling circuit and wind back the AC....

 

sounds quite similar to the words above by TomsFocus

 

Thank you that makes sense