I found the system out of refrigerant and the outdoor unit was in a low pressure lock out.upon visual inspection I found oil residue on the indoor coil. This along with the age of the system would point to a leaking evaporator coil. The outdoor unit is not work at this time, I explained the emergency heat function of the thermostat to the tenant. Due to the age and status of the indoor unit , I highly recommend replacing the indoor unit and getting a manufacturer parts warranty for the new indoor unit. I will type up an estimate for basic leak search options. Perform an electronic leak search. The system is completely empty and will require adding refrigerant to try to perform an electronic leak search. If the leak search results is inconclusive, we will not charge. There is obviously a leak though, the next step after electronic leak search would be escalating to a dye leak search. I highly recommend system replacement,due to the age of the system parts maybe obsolete. I have techni