Thermostat RTH230B not shutting off with ac on 2 wire thermostat RTH230B but have cold air&FAN IS RUNNING

You need 3 wires to run ac on that thermostat correctly. One hot leg to RC one to green for the fan and one yellow for the a/c control. Some in the past have tried to combine the yellow and green under one lug or wire but that does not work with a digital thermostat.

It can be wired for 2 wire a/c use only BUT you cannot use the green/blower connection at all so your blower has to be controlled by another means like a relay.



SEE here.


http://customer.honeywell.com/techlit/pdf/69-0000s/69-1800.pdf