Hi, I have a Heil furnace, model #NDGE105LF01. Recently my heater will has stopped igniting on its own. I can hear it start and it sounds like the gas is flowing but the pilot light will not ignite. I have to ignite it manually. Once it is ignited, it is not guaranteed to stay lit. I have to keep checking it. Any suggestions would be very helpful.

Thanks.

Most likely the thermocouple needs to be replaced &/or the pilot burner needs cleaning.