It must be an air transfer heat pump if it is on the roof. Just ask him to
check the condensor coils and evaporator coils and air filters to make sure
they are clean. Also check fan belt tension for proper airflow through the
evaporator coils and perhaps check the condensor fans to make sure they are
working. Also grease any fan bearings or oil if it is the case and they aren't
sealed. Also oil or grease any motor ebaring that aren't sealed variety. Once
all of that is good to go then an amp test on the compressor and a pressure
check on the lowside and high side are done that is it for preventative
maintenance...from there if it doesn't work properly it is a repair diagnostic
and troubleshoot plus repair...
It may also have electric heater coils that kick in if the temp gets to cold to
enhance the heatpump functions..he can manually test the coils if need be. If
nothing is borken you are looking at 2 hours labor tops or he is screwing you.

candice