I have a Goodman brand GMS8 model. The blower will come on but the flame will only come on in short spurts. It won't stay on long enough to heat the house. I checked the thermostat. What else can be the cause of the problem? This model does not have a pilot light. And I purchased a universal Thermocouple. It appears that my model has some sort of electric igniter. The gas comes in through a tube strait to three burners. The thermocouple is a copper tube for the gas however, what I see on my igniter, it is electric only. HELP!

Sounds like the flame sensor is dirty/oxidized. This is a pretty easy fix. You will find it located at the opposite end of the burner assembly from the ignitor. Remove it and clean with fine sandpaper or steel wool.