Outside compressor Goodman r22 5 ton installed 2013 worked great. Inside attic unit rheem electric heat M ac coil installed approx 1997 During the day "attic heat" the inside delta T is 2 to 4 degrees inside, cooler at night the delta T is 15 to 16 degrees. I cleaned outside compressor. I changed inside filters. I check for airflow leaks. I check compressor Freon unit seems cold and functioning. I tried to clean M coil in the attic. Sunction line going into coil is cold. Vent air has good air flow. I assume either the coil is blocked dirty, so I tried to clean again using AC coil cleaner. Made no difference. So I assumed Freon expansion valve is not functioning. Coil is a M coil and I can see no expansion valve, looks like spider tubes come right off the Freon supply line. I have tried to get the local AC contractor to come out but have been stood up on three different appointments. I know enough to follow directions just need a little advice.

Your attic temp is what 125 degrees? Not a surprise it doesn't function as well as night. Radiant heat load is almost impossible to overcome in summer conditions. Maybe it was cooler last summer. Have you checked pressure levels?