Haier HG93A0803 furnace starts combustion fan, igniter lights, flame starts, then stops after about 4 or 5 seconds. I replaced flame sensor and it seemed to work, so I left house (mother's seasonal vacant home). Next day same problem, so removed flame sensor and cleaned w/steel wool, reinstalled and it lit and stayed on a couple minutes, so I left again. Today, same original problem. Any suggestions?