Have a 2020 F-150 STX Supercab, which was bought new in September this year. Discovered wet carpet in the driver's side rear corner of the cab, behind the seat.
I use this area as storage with an aftermarket latch release installed to the seat latch, since it doesn't come from factory with such.
The carpet gets wet enough to soak a few paper shop towels that I placed in the corner to troubleshoot the amount and try to determine other contributors to the issue,
Made an appointment with the dealer to have their "water doctor" look at it. I told the service manager that I felt this should be a warranty issue, since it is so new.
I have read a few online items that suggest factory issues with the rear glass seal or the third-brake light area.
Anyone had any issues with this on your truck?
Thanks!

 

Yes, some have had issues.

Of course it's a warranty issue.

 

Yeah I get it at the car wash. Going to investigate it this weekend.

 

I just finished dealing with this same exact issue/problem on my 2016 F-150 XLT. It ended up being the rear glass. They can't re-seal it, needed to purchase a new piece of glass at $800.

 

Even a glass dealer like Safelite couldnt seal it?

 

Nope...the dealer doesn't even do their glass work, they sub it out to a glass shop. I don't know enough about the window to describe why the same piece of glass can't just be re-sealed.

There are a growing number of F-150 owners also experiencing sections of the rear defrost quit working. Apparently these can't be fixed either, and a new glass is needed to rectify.

 

I have a 2013. My water issue was seal on 3rd brake light. Apparently a popular one too. My rear defrost hasn't worked in years either.

 

When they were looking for the leak, the 3rd brake light was the first place they looked and re-sealed. Very common entry point.