I know this topic keeps coming up and I did do a search but did not find an answer that helps me (probably my own stupidity). I bought my 2000 f150 xlt used and both locks were sluggish but would not lock/unlock doors at time of purchase. I replaced both actuators and the locks worked great for about two weeks. Now they are both sluggish again and will not lock/unlock either door UNLESS it is 20 degrees outside at which time they both work. I'm hoping there is someone out there that can shed some light on this topic for those of us who grit our teeth every time we have to walk around or stretch across the cab to unlock the doors.

 

2000 F150
4.6L V8

Having the same exact problem. Problem started about 3 months ago.