Spring Residential Air Conditioning Repair Service. The technician arrived and found that the back right a/c unit was not running. The technician climbed onto the roof and ran a diagnostic of the unit. High voltage power was found to be working. Low voltage was found to be functioning at the transformer. 24 volts were found on R but no voltage was found on G. Board was not sending 24 volts to the contactor and therefore not engaging high voltage. The technician will need to contact tech support to confirm whether the board or thermostat is the cause of failure. A follow-up call will be scheduled ASAP. The thermostat was found to be functional however board was not sending out a command signal when prompted. Until a separate diagnostic board was used the system ran as designed. Board ordered will follow up with the customer when it arrives.