2018 Fiesta ST temperature still rise fast when idle with upgraded radiator

[MaxY]

Hi everyone, I live in LA and My 2018 fiesta ST's coolant temperature will rise very fast when stopping at light or idling with AC on. It will go all the way to 230 and I suspect it will eventually overheat if I let it stopped long enough. And when stopped the AC will not blow cool air. But as soon as I am moving, the temp will slowly fall back and the AC will immediately blow very cool air. I have already upgrade to CSF triple bypass radiator and when driving normally the temperature stay under 190 with ac on full blast so it seems the system is working at this when moving. But once stopped and AC will start blowing warm air and the temp will slowly raise. Has anyone else experience similar problem? what else can be faulty? I just checked the radiator fan and it is working. the car is bone stock except the radiator. Appreciate all the help, thank you all.

 

[M-Sport fan]

You have to check the fan relay, and if that is fully OK, or you still have the climbing temps, the fan module/controller or any of the connectors/harnesses going into or out of it may be corroded, faulty or burned/melted.

But first thing, even before any of the above is to check to make sure all of the connectors are fully seated and plugged into their receptacle sockets correctly.

How long ago was the radiator replaced, and did you do it, or was it installed by a shop.
DIYers, as well as shops have been known to forget to plug all of the fan connectors back in properly, resulting in your problem.