When you change your fan speed it stops blowing... When you turn DOWN (not up) the thermostat (Cooler is DOWN don't you know) the fan comes on with the compressor..
Ok, fans usually have either 3 or 4 settings on RV
HIGH (Which I HIGHLY recommend)
medium (optional, the 4th setting)
LOW and
AUTO
If you change it to AUTO, you are describing normal operation
IF your T-Stat is wired.. and it works on either HIGH or LOW as you feel it should (Runs all the time) but on the other mode it does not.. Might be a broken wire or a bad T-Stat. (or a bad relay)
Mine.. Blows just fine, all modes.. problem is lost refrigerant in the coolign system, Been over 2 weeks with only one AC in this 38'er... And it's getting HOT again outside (the 1 week was record setting, EVERY DAY we set a new record for consecutive number of days over 90 degrees.. Eating dinner out cause I can't stand the heat in the Kitchen is getting expensive.)