Gas and Oil Home Heating Furnaces - wall furnace shuts off

I have an old dearborn gas double wall gas furnace. For some reason it just shuts off and the pilot light also goes out. I have cleaned it thoroughly, replaced both the thermocouple and the gas valve. I still have the same problem. I have tried turning the thermostat (heat only) up and down. The system works fine but after about 15 minutes the burner shuts down and the pilot light also goes out. The pilot flame is blue when burning. Any suggestions? Though the unit is old it is seldom used. Thanks for whatever help you can be.

It sounds like there is an interruption in the gas flow between the meter and the furnace. Either that or there is a draft blowing out the pilot light. Even if the furnace should fail, the pilot should stay lit.

I have an old dearborn gas double wall gas furnace. For some reason it just shuts off and the pilot light also goes out. I have cleaned it thoroughly, replaced both the thermocouple and the gas valve. I still have the same problem. I have tried turning the thermostat (heat only) up and down. The system works fine but after about 15 minutes the burner shuts down and the pilot light also goes out. The pilot flame is blue when burning. Any suggestions? Though the unit is old it is seldom used. Thanks for whatever help you can be.

You mentioned you changed the thermocouple. Was this actually a pilot generator? If yes, check the thermostat wires as they pass thru the furnace sheet metal. Sometimes the wire is cut into as the heater heats the metal and expansion occurs. When this happens it causes the pilot to drop-out. Have seen this a few times.

That's a very good point about those wires. They could easily be damaged.