AC blows cold when outside temp is mild (ex. in the 60's or low 70's)

So I’ve been having issue with my AC, but this week I noticed during the day the AC isn’t blowing any cold air but later in the dusk the AC started blowing cold air.

I’ve got another thread where my mechanic said my Evaporator has a small leak and tried some AC leak sealant but doesn’t seem to have worked. Now I’m wondering if it really is my evaporator or something else. Someone at work said my temperature gauge might be bad since during hotter weather it doesn;t work but does during cooler temperature