tl;dr;? see bold text
I recently inherited an old 1991 Ford F-250. It seems to run well, only has 80,000 miles, but it has two main issues (I'll post a separate question about the other one).
The one issue I'm trying to figure out right now is why the vents always blow hot air. I can turn on/off the fan just fine, but the vent always has hot air coming through it - with the exception of when the truck is not yet fully warmed up, I can get a little cold air from the A/C being activated. This obviously doesn't last long, as it turns hot when the truck is warmed up.
I'm not a mechanic but I've always done most of my own repairs/upgrades, usually from resources I find online. I haven't found anyone with this specific issue (but then again, my Google Results are contaminated with what appears to be a common issue with the F-250 vents that is different from mine).
Does anyone know what could be causing the truck to always have hot air coming out of the vents (when it's fully warmed up)?
EDIT: I doubt it's significant, but I updated the year to be 1991. Was wrong in original post, it's not a 1992.