I completed a callback service. Here because customer says he replaced the thermostat because the one We installed with furnace was too complicated. The thermostat is set correctly but I found the thermostat part not securely snapped to the back plate, also found three amp fuse blown. I replaced fuse and secured thermostat to back plate and cycled system. Checked refrigerant charge and found it just slightly under charged running at a 27° superheat. Checked 35/5 capacitor which checked out OK. (33.8/4.99) Contacts are starting to get worn. Compressor/fan amps are ok. Customer doesn't want to add refrigerant at this time says everything was running pretty good so he's just going to let it go. System is running on my departure.