Recently when it warmed up a little we switched back over to ac. The blower fan came on but no cold air. Fan on outside unit does not turn. It got colder so we put it off. Now the thermostat inside the house has been off last few weeks and sometimes we have to switch it off then back to heat for it to kick on. Starting this morning the fan kicks on and usually shortly after you hear the heat kick in. Now it only kicks in for a minute then kicks off and only fan blows. What is wrong now. Thanks.