3 replies to this topic

[obenourb]

8 year old natural gas unit has been reliable until recently when the pilot light expires without any externally identifiable reason. These facts apply:

• No changes to the surrounding environment (doors into the room the same, no ventilation changes, no new gas appliances in use)
• The thermocouple produces 24mv and the connection is clean where it screws into the gas valve. The pilot will hold after 6 seconds of heating and may go a whole day without issue.
• I pulled the pilot and thermocouple assembly and cleaned them good. No obvious damage. I blew out gas line with HP air to the extent possible through that tiny hole.
• I verified that while the furnace is running a few feet away that the hot water heater exhaust still draws smoke up the exhaust piping very strongly.
• Unit has never had any water damage due to flooding, backed up pipes, etc.
• The burner unit fins show some signs of cracking at the ends but I would not say they are bad and there was not a lot of debris on the bottom of the unit.
• The photos show the heater specs and the gas control valve specs.
• The wife unit is tired of cold morning showers and may replace the husband unit if not fixed soon.

The student is ready to learn at the feet of the master.

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[kdog]

Try a new Thermocouple

[Bullstok]

I second the changing of the thermocouple. Most pilot issues go back to the thermocouple. It is so often that its not worth testing or cleaning it for the most part (they are cheap and you do a service that most likely needed done anyhow.) Then also: Check that when the burner is firing main flames are stable and then when the burner shuts down that it is not blowing the pilot out or making the pilot flame move around much. The pilot should always remain strong. Check that the fresh air inlets on the bottom or around the sides are clean. Be aware that when the inner door is in place the flames act differently since fresh air comes in more through the door opening when the inner door is off. Try to have the door on as much as possible when looking at the flames. If not the inlets, the thermocouple, or pilot flame being weak or misaligned, the pilot light solenoid in the gas valve could be getting weak. FYI: Gas valves are generally considered non repairable and get replaced as a unit.

Edited by Bullstok, 15 January 2012 - 10:45 PM.

[jumptrout]

Another vote for thermocouple.