Re-settable fuse not blown at time of arrival. Customer informed me that he noticed the thermostat slightly off of the wall plate and that after he reconnected it, the display came back. System has 24 Volts to the thermostat. Opened the cover to the thermostat several times and discovered it is quite loose. Replacement of the thermostat would be going overboard due to type and cost. Recommending customer either leave cover completely open or pushing back onto the plate after every time touching it.