I have a five year old vent free gas log set in my fireplace. I only use them ocassionally or if the power goes out. I have cleaned them and tried everything to light the pilot light. It will light but will go out as soon as the button is released. The owner's manual says it could be the thermocouple or control unit needs to be replaced. Does anyone know who services these units or, because of it's age,should I just buy a whole new unit?