If replacing the blower motor resistor (under the passenger side dash, mounted on the front blower motor assembly) does not fix the problem, then the other likely candidates are listed below. (in your case, since both the front and the rear blower motors are not working, it is most likely #1 or #2, but it could still be #3. Hope its #1 or #2, which are both inexpensive to replace:
1. Blower Motor fuse. The blower motor fuse is located in the ENGINE COMPARTMENT fuse box (not in the inside the vehicle dash panel fuse box). It is the 40 amp (Orange) fuse located in the 4th position from the metal clip side. To open the box lift the plastic tab on the box end away from the box, until the lid lifts up. It is hinged on the other end. The 40amp Orange Blower Motor fuse is sandwiched between 3 RED 50 amp fuses on one side, and a 30amp and siver-metal-cased, and 20 amp fuse on the other side, in the central column of the fuse box. This is the most common failure of the system. You can pull the fuse with a pair of pliers, and inspect it. If blown, the metal u-turn shaped wire ribbon in the fuse will clearly have a burned break in it. Or you can test it with the continuity setting of a volt meter. A good picture is available at the URL below.
2. Blower Motor Relay. (Located under the dash, on the driver's side, to the RIGHT of the driver's steering wheel). It is in a block of 3 or 4 relays, see the owners manual for which one, or swap in a new relay to each of the 4 positions one at a time. All four relays use the same standard Ford relay component.) DO THIS STEP ONLY AFTER CHECKING THAT the FUSE IS GOOD (in step 1).
3. Blower Motor electronic speed control unit is bad. (under the dash on the passenger side behind the glove box. To get at this you must remove the glove box rear backplate (6 screws, 2 on the latch, 2 others on the top, 2 at the bottom on each edge. The one at the bottom console edge is hard to find, but its there.) Then unbolt and replace with a new electronic controller unit. Expensive from dealer, I would get one at a junk yard, self pull if comfortable with DIY, and otherwise pay more for it to be removed by the yard, or a yard puller hire-able employee.) Unbolt the controller, and unplug it, plug in and bolt in new one. ONLY ATTEMPT #3 if you have checked BOTH #1 and #2 first. #1 is by far the most common #2, next most common, the controller least common (but the do fail sometimes.)
on Jun 13, 2021