Customer is having an issue with the second floor heating system: This is a newly installed train furnace, coil, and condenser When there is a call for heat, There is chattering at the AL2 Control board and the outdoor condenser is turning on and off At arrival, the system is off- Visually inspect indoor and outdoor equipment and thermostat Call for heating from the second floor thermostat The furnace fire is normally and is on and running After a few moments notice chattering at the AL2 control board And the outdoor condenser is cycling on and off Found incorrect voltage at the furnace. between Y from thermostat and C - there is 26 volts with no call for cooling when Y from the thermostat and Y from the AL2 board are connected - The voltage is fluctuating 10-15 volts When checking between common and Y from the AL two board, there is no power Spoke with manufacturing and confirmed that system is operational and no issues with the equipment The issue is on the thermostat side And train