Your AUTO ambient light sensor for nite-time illumination...
C1BZ-13A018-A - It's called a "Sunload Temperature Sensor"
Works when the Light Switch is on AUTO (A)
So you are aware - there are two types of "Sunload" sensors, one works with
illumination and AC the other doesn't only does Illumination and does not affect AC. The one above is for NON-AC controlled vehicles.
How do you know?
You have two types of "Climate Controls" for the typical Fiesta -
and
So when and if ever you need to get another Sensor - know the Climate control system too, for it "looks" at the Auto system for communications and setting of temperature. As to keep the interior at your set temperature as well as knowing how much light and heat there can be. This is done so it knows how to form a budget on engine loading and tries to adjust for the demands accordingly.
So the OTHER ONE is this...
C1BZ-19E663-A
Same top dome shape as above, but has a LIGHT GREY body color
It also has a lot more pretty little pins on the connector - and an index, to show that there is only one type of connector system it works with so it cannot be swapped in error with other systems. So if the connector index doesn't match the connector on the vehicle - it's not the right sensor - find the other type - listed above in this post.
The big clue is the BODY of the sensors - the color is different between the two.