When you're paying off so much quicker, it's less about interest rate and more about interest cost over that condensed timeline. 

A few months ago, a neighbor told me that there were a few A/C condenser units stolen in the area.

I'll save you the hassle of exploring markets and information as I have it all condensed into one form for you with markets you didn't even know were cash cows.

You are just fixing the air handler if the outside condensing unit is in good shape you may get a few more years out of system.I typically pay under 4k for a complete new all electric split HVAC system.

If you have not done so, use a garden hose to spray out the condenser coils/fins.

They're a self contained heating & cooling unit that is ducted like a traditional system but doesn't have the additional refrigerant lines and condensing unit like traditional AC. 

It gets to roam freelyThere isn't a room in the house where they can just barricade the dog and there are no doggy doors.Ages ago, a dog pissed on the central a/c condenser unit outside, and the coils corroded .

Sounds like condensation. 

Eligible on select products in the following categories: indoor air handler/furnace, outdoor condensing unit or heat pump, ductless mini-splits, package units, and boilers of eligible brands including Rheem®, Carrier, and Lennox®.

Also immediately buy and set a lease addendum that you need working leak detectors in every leak able spot (under bathroom and kitchen sink vanities, by dishwasher, by washing machine, by hot water heater, by ac condensate line, anywhere basement might flood ( near sump pump).