Get the right size filter. Should be a no brainer but it happens a lot.
Don’t use a thick allergy filter it will ruin an old fan motor.
If the furnace door has to come off be sure it is replaced tight there is a switch that will turn off the unit.
The filter rack should have a door. If not the hot air from the attic will increase the temperature.
No washable filters some are to thick other are to thin.
Change them every month. No 90 day filters a cheap filter more often is better.
Buy 12 at a time so you don’t run out.
You should have a check up every spring .
Aaac service heating and air Mcdonough repairs residential furnaces and air conditioners in McDonough, Stockbridge, Locust grove, Jonesboro, Jackson