Mine is still at the dealer. Will report back if they find something.

 

I have been experiencing this same thing for the past 12 months. It has been back and forth to the dealer and they are trying to figure out what it is but difficult due to its intermittent nature. Please keep us posted if a repair is found. 2013 FX4, loaded. Going back to dealer later in week.

 

Mine started doing this this summer. Same exact thing lower settings work, anything above 4 or 5 will shut it down. At first all I would have is one speed, about "3" on the manual fan setting (Climate controlled system) turn the fan down no speed change, turn it up no speed change, I went ahead and replaced the resistor pack with one from O'rielys and now I have control from 1 to 5, but anything higher than that it shuts down. Don't really want to start throwing $$ and the problem hoping some "part" fixes it.

I thought I saw a thread on here where it ended up being a PCM problem, but the dealer still couldn't fix it, and they ended up buying back the truck from the guy. But I'm beyond that option now.

 

I got my truck back after a month. They ended up putting in a new AC Blower motor. Have my fingers crossed. So far so good.

 

I replaced the Blower Motor and Controller with Motorcraft parts purchased from Amazon this past Wednesday 8/19. Everything has been working fine so far.

MM1094 Fan and Motor Assembly
YH-1829 A/C Blower Motor Switch

 

I purchased a new Blower motor controller at Ford dealer as I was only able to get level 1 before it shut off. Once I had the part in my hand my HVAC miraculously began working again and has been for 5 weeks now. I've got the part in my center console. This is a weird problem and I think it is electrical/computer driven. I doubt changing the blower motor or any major components will fix this.
I had an issue similar to this on my 2002 silverado, turns out it was a loose fuse, my thoughts are the same here. When ramping up motor speed there is a wiring or fuse connection that is bad and it cuts out. That is also a reason it gets worse over time and why replacing a part fixes it for a while as you must jostle a wire or connection somewhere while working on it.
My FX4 also has the front speakers that cut out due to a bad connection from the crappy wiring clips on the harness. you turn the volume up and they start working again.

 

OK, Got my truck back from the dealer and they now replaced the blower motor. It has been working for over a week now. Last time they replaced the resistor and it only worked for a couple days. Weather is starting to change cooler so I may never really know if it is fixed until hot weather again.

 

I'm still working fine. Looks like the blower motor in my case. Have read several other cases with the same result. Hmmmm. Defective batch? In any case, its FIXED!!! (knock on wood). Now I can put the tune back on...

 

Has anyone figured out an answer for this my 2011 is doing same thing, has new fan motor and resistor, still kicks out on setting 5or6, on and off on and off on 4 runs fine

 

My 2013 KR started shutting off again. Dealer could not replicate it at the shop (figures - it is intermittent). I had them replace the blower based upon the posts here. Since this is the third time in for the AC shutting off, I hope this does the trick. Fingers crossed.