Was working on weather master carrier 8000 today and opened up the plenum to find the access panel to the evaporate coil missing can this cause the a/c to not work correctly? It hasn't been an issue to this day but I'm concerned about this....
I doubt anyone would notice the possible effects of a missing end plate. It might allow return air to bypass the coil which could lower the supply temperature and the efficiency of the AC.
I'm not familiar with the unit but a sheet of tin would be a fix.