I am not in the business but a friend has a problem and I'm usually pretty good with being a weekend handyman. This one has me stumped however.
Eight year old colonial with an Aire Ease Ultra V unit in the attic for second floor HVAC in NY. Friend tells me that during the day, everything is ok and furnance works to keep heat at set temperature.
However at night, the furnance will not put out sufficient heat. He has changed out the thermostat and same problem occurs. He has attempted, with both old and new thermostat, to override settings and "hold" temp at 68 or 70, but can't get the furnance to get second floor above 62. First 7 winters never had a problem.
In the morning, everything goes back to normal and furnance heats the second floor normally.
Other than telling me the house is haunted -- has anyone heard of this?
BTW, he has a service contract with a local HVAC company -- they've been to his house and they say everything "checks out" and they have no idea what is wrong -- suggesting he needed a new thermostat (but he had already changed it by then).