This mini-split system is located inside the first floor electrical room. During maintenance it was discovered that the thermostat that serves this system was not responding. None of the buttons worked when assembled and when disassembled and checked there were signs of corrosion. A verbal quote to replace the thermostat was approved by Ryan today. A new thermostat and the sender unit (wireless system) that pairs with it were sourced, picked up and installed. After install the thermostat was programmed to match the system. It was then operated and the temperatures were in their proper ranges. The outdoor unit was visually checked for any error codes and any possible deficiencies. This system is back in service. Of note is that this system is a cool only system. Thank you, Jon Tech notes: Mitsubishi mini-split system Ground level electrical room (west) S/n ending 1154 Temp split 20 (78-58) New wireless t-stat and relay module