Warm temperatures are rapidly approaching. Now is a good time to prepare. The first thing you should do is check your furnace filter. It is used in the heating and cooling cycle and can affect the efficiency of the system. Be careful when choosing an air filter. Stay away from the high merv rated 1" filters. The higher merv rating should only be used with a 3.5 to 5" thick filter due to restriction issues. The higher the merv rating the more dense the air filter is and the more restrictive it is. Slowing the air flow down can cause damage to the system and will cause increased operating costs.
Shortys HVAC Supplies in West Newton IN sells high efficiency air filters and repair parts. The phone number is 317-821-8770 and the website is https://shortyshvac.com/ They are good guys to deal with and they do ship.
I used to work there but I am now retired.
If you like stuff like this let me know and I will try to post more tips.