Have a 2 yr old Carrier Heat Pump/ Honeywell Thermostat.
When I turn the fan to the ON position, no matter where I have the thermostat set, or even with the system set to OFF, the unit continues to cool - the compressor is on all the time the fan is running.
COntacted Honeywell - did diagnostics on THermostat - it is OK. Even wired to bypass the thermostat, and still the unit Cooled whenever the fan was ON.
Contacted Carrier - they told me to contact Climate Master, who makes the Water-source heat pumps for Carrier. They've been totally nonresponsive, but I see nothing on their website that looks like my unit.
Two A/C contractors have been unable to find a cause for the compressor to be ON whenever the Fan is ON.