Code 12 on my weathermaster 8000 furnace said (R-W closed) what is R-W

R-W means Red-White. In English, it means your thermostat is calling for heat. If you power up your furnace while the thermostat is calling for heat you get this code.

Try flipping the thermostat to the Off position and then removing power from the furnace for a few (15) seconds. When you restore power, the code should be gone.

Hope this helps,
WallyH