I have a RHT2300B Honeywell Thermostat and my AC won't shut off when it reaches desired temp. It will be 72 and I will set it to 71. It keeps running and it will be 69 and it won't shut off. Seems uncommon. My wiring in the thermstat is the Red into R, Green into G, White into W, and Light Blue into Y. The only other terminal is the O/B and I no that's not supposed to be used. Before I had a White Rodgers thermstat that came equipped with a different wiring panel that had a Rh/RC jumper wire and I never had any problems with my AC or heat not cycling or turning off. Any help or feedback is greatly appreciated.

Hi

As you mentioned , used terminals are R,W,Y,G
In this R is power,W is heating ,G is fan and Y is compressor
In RTH2300B when you run Ur cooling,do you see word cool on on display,if cool on is there then that means the set point has still not been satisfied.
If cool on is not there,then you may try these steps
1) put your system switch to off fan to auto
If compressor is still running
Then remove face plate off the wall
If compressor is still running then remove Y wire out
If compressor still running then its your compressor for sure
But , if your compressor stops as you put stat off the wall
Then remove Y and G wire out
Put G to Y,leave Y wire unconnected
Put stat cover back on wall
Put your system to cool fan to auto
If fan starts running ,then it's the stat
But if stat behaves normal,fan comes on and off as you call and end the call for cool
Then its your compressor

Try this
If still cannot figure out
Call Honeywell Tech Support.

Check to see if your contactor in the ac unit is stuck