2018 Ford F-150 — a/C is cold on the highway but warm at stoplights

I'd want a measurement, not a hunch. Swap the cheap/easy piece first on the 2018 Ford F-150 and see if the fault moves. You'll know quickly if you're on the wrong tree. This is from a 2018 Ford F-150 in Baltimore with 104,000 miles. I'd want that in writing, not as a promise. I'd sleep better after that step, even if it finds nothing. If that fails I'll eat the diagnostic fee.