The fan on the thermostat continuously runs, even if it's set on "auto". I have to shut off the main switch in order for it to shut off. But once the air kicks on, the fan stays on until I flip the main switch again. Also, the error code on the main board reads Reversed 115 VAC polarity... any ideas?

The fan on the thermostat continuously runs, even if it's set on "auto". I have to shut off the main switch in order for it to shut off. but once the air kicks on, the fan stays on until i flip the main switch again. also, the error code on the main board reads Reversed 115 VAC polarity... any ideas?

The reverse polarity usually means that the line and neutral are reversed or it is possible just the transformer feed wires are reversed. Sometime these type of problems can be very difficult to find.