Hi all, I am looking for some advice/guidance please! My wife has a 2011 1.6 TDCI Fiesta MK 7 Titanium with Climate Control.

When the heat is turned to high, it'll warm up before blowing cold and regularly go back and forth between hot and cold. If AC is lit up, it'll seldom get hot. I did some research and it suggested the sensor behind the dashboard near the knee area.

Before I started, I did some live reads with FORScan which returned the following odd results.

With the engine off, eletronics on - the ambient air temperature read at 214°C (wrong) and the in-car temperature showed 0°C (also wrong).
With the engine running, ambient air temperature read correct at 11°C and the in-car temperature showied 214°C (wrong).

I've cleaned the grille with compressed air and removed/cleaned the internal temperature sensor (part 3M5T19C734AB). With the sensor behind the dash unplugged entirely, the same results above were returned in FORScan. I'd of expected a 0°C/error return with the sensor unplugged entirely.

I haven't been able to get at the outdoor sensor due to it's irritating location behind the front bumper, but I'm wondering if anyone has seen this before alongside the climate blowing hot/cold when on high before I look at taking the bumper off and replacing both sensors. Any advice/guidance appreciated!

The most probable cause is the internal temperature sensor has failed. The open-circuit value of the sensor would give the maximum temp possible (214^oC)

15 minutes ago, unofix said:

The most probable cause is the internal temperature sensor has failed. The open-circuit value of the sensor would give the maximum temp possible (214^oC)

Thank you. I'll get a price for a new official part tomorrow. 

Unfortunately a new replacement part has made no difference. The issue is still exactly the same. I wonder if it's worth changing the external sensor before considering a Ford specialist as the wiring might be duff.