I Have a Rudd Heater it has a electronic ignighter it comes on lights the flame, but the flame will not stay on, the heater runs but the flame comes and goes, it will not stay on and heat the house

I Have a Rudd Heater it has a electronic ignighter it comes on lights the flame, but the flame will not stay on, the heater runs but the flame comes and goes, it will not stay on and heat the house

Just a guess since no model number try this.