I am tryig to install a two wire thermostat in a mobile home. The wires are not marked. It is a manual 24 volt thermostat with markings G,Y,W,RH,B,O,RC with RH and RC already connected. It is a red and white wire going to the blower that connect red to red and white to green. Please HELP!:confused:

If you have a red and white wire at the thermostat, connect the red to RH and the white to W. That should give you heat. If it is a digital thermostat, it may need a third wire from the transformer at the furnace connected to the B terminal. The red wire already comes from the other side of the transformer.

It sounds like you are trying to connect a heat pump thermostat to a two wire furnace only system. If this is the case connect one of the wires to R on the thermostat and the other to W on the thermostat. It is only acting as a break in the wire and does not know the difference in the colors. If later you add air then you need more wires and the colors will mater.