We changed a white rodgers thermostat out to a honewll round and now in order for the heater to come on you must first turn the fan to the "on" position. The heater will come on but won't turn the fan on so the safety sensors turn the heater off when there is no air flow. I was told that we got the wrong thermostat. That we had to get one that had a common on it. This is a 5 ton A/C unit with electric heat. I did not personally change the stat so I couldn't say if it was a 4 or 5 wire setup. If I turn the fan to the "on" position the heat works fine. The A/C works as correctly. Can someone advise?