First, look at the obvious things. Is the a/c actually running. If it is and the a/c bely is properly tightened, you may need to add the chemical coolant to the system.
Low refrigerant defective pressure switch
tad bit low on freon.
if its blowing, but not blowing cold its low on coolant. it takes r134a.
freon needs to be charged
the blown head gasket would make it over heat. but it wouldn't cause the heater to blow cold, it should actually blow hot if that is wat happened
because you need to keep warm when it is winter and other times when it it cold
yes
heat core. leak. thermostat. no antifreeze.
No, not if it's on a heat setting. Most home thermostats have a "Fan" setting that will blow cold air if the attic is cold.
Check temperature control cable for binding.
Low refrigerant causing compressor not to start?
It doesn't really blow it out it just warms the cold air.