The thermostat is the round type. (pic attached.) The thermostat is set to the max. The furnace will run...but will not raise the temperature above 65. It seems as though the furnace is doing its part. The blower is working and the air is hot coming from the ducts...it seems as though the thermostat is haveing trouble communicating. We tried to replace it with a digital...RTH2310B; but we have a two-wire system and this is for a four-wire system. Will it work...and which two connections do we use?