Washed all filters Inspected all indoor coils and blower compartments Checked all heads in high heat mode Living room 115 supply Left bed 119 supply Right bed 118 supply Checked and tested drain lines Checked electrical connections and safeties Rinsed condenser coil While on property indoor heads started flashing 76 error code indicating outdoor unit operating valve thermistor error. Contacted tech support and found that the thermistors at the condensing unit had gone bad. Replaced thermistors and started unit. Unit started up with no issues and was not flashing any codes. Unit is working properly Recommend cleaning blower compartment in master bed