2012 dodge avenger

[SEP1981]

I have a 2012 dodge avenger, had the actuater replaced couple weeks ago. this is under dash hooked to blower moter. since it got cold outside, i had only little heat on drivers side cold air on passenger side. I was told it was stuck thermostat. I changed that still same thing. Now i was told there is air pocket in heater core. it needs backed flushed. I took off top hose on heater core, let it drain some, but still the same thing, does actuater have anything to do with heat? or do i need to really back flush system, thanks for your help