For AC systems I have a wonderful local AC company in my town do two services a year... one in spring and one in fall... they make sure the filters are replaced, blow out the condensation drains, clean the coils and make sure all is well.

All new fixtures. 5000 Replace improper basement ductwork 3225 A/C coil and condenser 3200 Stairway into basement - bring up to code 2250 Washer/Gas Dryer (stacked) 1800 Paint throughout 1500 Transfer taxes 1200 New carpet - stairs and both bedrooms 1000 Gas water heater 800 new fridge 800 Exterior paint 800 Demo/creation of fridge location 725 Replace wood rot along roof line and cap with metal 700 Roof coating 700 new gas stove 600 Trim repair, doors for both closets, door for 2nd bedroom 500 Window blinds throughout 300 Minor siding repair - rear 200 New screens 150 Total costs 34200 Offer ALL CASH 21799

Cleaning the air handler coils when dirty, changing filter, using A\C pan tabs, blowing out the drain line with shop vac and using chemicals to deter growth in drain lines all seem to help. 

Things like refrigerator compressors going bad (often from running too much because of dirty coils) and similar are too hard to prove, so you just consider it a cost of doing business. 

Did he tear the A-coil out too???

Also, something may have seeped past interior panels onto coils or some other less than obvious location which gets pumped back in.

Refrigerators will usually last if the landlord does a little maintenance on them and keep the condenser coils clean, they are now under the machine, rather than on the back, so they get all the crap off the floor on them.

It could be a lack of proper air flow around the coils, the condensate not draining away properly or draining too slow, the refrigerant could be too low or leaking, the air filter could be clogged, a damaged or broken fan, etc.

That one is used for unclogging the pipes, but it's not great for a toilet b/c it will scratch the porcelain.The second kind looks like a broomhandle with the coil coming out of one end, and a crank handle on the other end.

I have seen more evaporator coils than any person should.