Very sorry for the long post but since this is a complex problem I wanted to be thorough in my description :D
I have an older HEIL EG100-1 Natural Gas forced air furnace in the garage in a house I just bought about a month ago. This furnace was rarely used (from what I can tell) by the previous homeowner. The furnace employs an oldschool standing pilot light with thermocouple right beside it.
Here's the problem:
The pilot light goes off after one heating cycle.
Here's the order in which it all goes down...
1. I light the pilot with the red button depressed
2. The pilot lights and heats up the thermocouple
3. I let go of the red button and the pilot stays lit until I call for heat from the thermostat
4. The burners kick on and after the plenom gets hot, the blower blows the hot air out
5. The thermostat heats to the temp I have set it at sending a signal to gas valve to shut the burners off
6. The burners go out but the blower is still running
7. The pilot light goes out by itself (happens at random times but usually after the burners are shut down by the thermostat control)
I don't know why this pilot is going out by itself.
I have changed the thermocouple and since the unit kicks on after lighting the pilot, I assume that this brand new thermocouple is functioning correctly.
I have also used a multimeter to verify that the thermostat is functioning correctly. It is and 24 volts are supplied to the gas valve when called for.
Possible reasons I can think of for the pilot valve to go out:
1. I have cleaned the end of the pilot valve and replaced the thermocouple. The pilot flame looks large enough and the flame hits the end of the thermocouple directly.
2. There are no drafts around where the pilot is located to blow it out.
3. Gas is being supplied to the pilot as well as burners because it kicks on initially.
4. Thermostat is functioning correctly (verified with multimeter) but shouldn't have any effect on pilot light anyway.
5. Just for good measure, I've replaced the dirty air filter with a new one.
Do I need to get another gas valve? These things are incredibly expensive from what Ive researched. Is there any way to remove and clean the Gas valve? This furnace has not been used for a while and I suspect some spider nests or other debris in the gas valve itself.
Any suggestions before it gets wicked cold would be greatly appreciated :)