We are replacing a Honeywell rotary dial thermostat with a RTH221B honeywell 7 day programmable. We hooked the 4 wires to the thermostat according to the diagram on the instructions. The fan will run in the fan on position,but neither AC compresor nor the heat will start up. Is there a way to test the thermostat to see if it is good? What other problem could there be?