Not pushing heat out while idling or sitting at lights

So have a 2007 equinox awesome vehicle but has never
gotten really warm in the vehicle during winter months. My
sister originally got this vehicle with only 40,000 miles on it
and getting close to 200,000 on it. She was never able to
get it hot inside in the winters either. We have done
thermostat changes and since acquiring it my husband has
"burped" the system which seems to work for a little bit but
always happens again. Help at ends wit I hate cold.
Sometimes the fan does not kick on either. Otherwise
always dependable and has always started so don't want to
get rid of it.