I just installed a Honeywell RTH230B thermostat. Connected the four wires, per the instructions - Red to Rh (jumpered to Rc) White to W, Yellow to Y and Green to G. I live in Arizona, and have a split air conditioning system. The Air conditioning compressor unit turns on, the fan blows, but no cold air comes out of the ducts. I get a trickle of warm air that is being recirculated by the unit, but nothing else. The thermostate I took off was a Robertshaw, and the wiring was connected Red to Rc, Green to G, White to O and Yellow was connected to both Y and W. Any ideas what I'm doing wrong?

Is your unit just air conditioning or is it a heat pump? With the yellow wire connected to both Y & W tells me it's probably a heat pump, if so is your new thermostat for a heat pump? The white wire went to O on your old thermostat and O usually energize the reversing valve on heat pumps.

If you need more help, see the sticky at https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html. It has sections on both identifying a heat pump and thermostat wiring.

I just installed a Honeywell RTH230B thermostat. Connected the four wires, per the instructions - Red to Rh (jumpered to Rc) White to W, Yellow to Y and Green to G. I live in Arizona, and have a split air conditioning system. The Air conditioning compressor unit turns on, the fan blows, but no cold air comes out of the ducts. I get a trickle of warm air that is being recirculated by the unit, but nothing else. The thermostate I took off was a Robertshaw, and the wiring was connected Red to Rc, Green to G, White to O and Yellow was connected to both Y and W. Any ideas what I'm doing wrong?
Sounds like you had a make shift job from the get go. If you do not know if you have a heatpump or A/C turn the power of to the out side unit and remove the electrical cover.(Just two wires from the stat= A/C only- 5 wires or more= heatpump)Give more info we will try to help.