If you are looking for replacement parts or professional service, referencing is often more helpful than GE. Many internal components (like heat exchangers, burners, and blower wheels) are cross-compatible with early Trane models. If a technician tells you they can't find parts for a "GE," ask them to cross-reference the part numbers with Trane inventory from the late 80s and early 90s.
Disregard the "RAR" when searching for documentation. Search instead for the General Electric 21LU Series Manual or GE 21LU060A2M1 . The internal schematic for the blower motor, gas valve, and limit switches will be identical. general electric furnace manual model 21lu060a2m1 rar
Ensure the thermostat is set to "Heat" and the temperature is higher than the room's current temp. Check the emergency shut-off switch (looks like a light switch) on the side of the unit. If you are looking for replacement parts or