There are two relays for the fan.
One, the AC the other is the Radiator Cooling Fan - one is controlled by the AC so to hear it click on that is a good sign that the system is functioning for it uses the "same ground wire" only thru two different relays.
So, this just means you may have to replace the Cooling Fan Relay - which HAS A DIFFERENT SIZE LUG in its pinout...
Below is for POST 2012 Fiestas'
The one with the New Nose Job with the new Chromed Grille fascia
The older 2011 and earlier Fiestas have a sloping front grille nose with same color as the body paint job.
To find the AC Fan Relay - just turn on the AC and the relay for the fan that runs thru the AC Circuit will engage and you should find it relatively quickly and note the pinout PIN sizes are different - so you know.
- The Above is from a 2018 Fiesta - 2011 Has a Fuse Box in same area only as a different shape
Grab your owner's manual - locate the FUSES section and follow along...
See the "schematic" on the relay body? There are two sets of contacts a
low-power switching side that are AMBER ARROW, and the SWITCHED LOAD side - the fan uses the SWITCHED LOAD side - and needs about 20 amps - so if the AC Fan works - the Relay for the Cooling fan would just need to have the SWITCHED LOAD Side briefly shorted to hear the fan click on - if it comes on - the relay is bad - if it doesn't the Fuse to it is blown.
If you have a continuity checker or Voltage tracer tool, the relay and blown fuse should be easy to spot.
To add more
See the F16 Fuse?
That is for powering your A/C Relay and for the A/C COMPRESSOR
the Cooling FAN will not kick on in A/C if the F16 Fuse is blown!
(
It powers the system to engage the Cooling Fan Relay)
