Q: Resolution changed on remote display.  Fan runs at HIGH speed.

Today, for no reason, resolution changed on remote display.  Option needed no longer shown.  Tried SMC and PRAM resets.  Now resolution on the MAC AIR is messed up (not full screen) and the fan runs at HIGH speed.  This is a sudden change.  Have been using the MAC Air in this exact configuration for 2 years.  Tried restart/reset of monitor.  Nothing.  Did resets on MAC and screen changed there.  Also the fan runs at high speed.