Ugh, Every season, when I switch from heat to air, neither one works. I've had repair men replace pratically everything. Now it's AC time again, outside compressor is on, inside is not. Switched to heat & that comes on, so it's not the fan. I have new batteries in thermostat, usually it will kick on eventually, hopefully before the compressor freezes up. Any suggestions? It's a Goodman GMP-075-3-Rev. P.S. I've had the fan motor replaced, mother board, etc

The blower should come on the same time the A/C kicks in. (rule of thumb if a time delay is not used). Can you turn the blower on from the thermostat if you switch the fan to ON? If no, you may have a bad thermostat or blower relay bad for cooling. Some systems use 2 speed blowers 1 for heating and 1 for cooling, if a relay goes bad you may have blower action in one mode but not the other.