2oldman wrote:
I just did a test on my Atwood oven.
Left pilot on, went outside and turned off gas. Pilot burned for a few minutes then extinguished. No gas smell. Turned gas back on. Immediate strong gas smell in the oven.
So, I guess that means the thermocouple doesn't work or never existed in the first place.
Thermocouple did not have enough time to "cool down" with your test.
Needs a few minutes to cool down.
Thermocouples are basically self generating a small voltage when there is considerable amount of heat like a direct flame on the tip.
In essence you take two dissimilar metals and make a junction of those metals. When heat is applied to the junction a small amount of voltage is generated.. A thermocouple contains multiple junctions in series to get enough voltage to operate the gas valve.
That voltage is just enough to hold the pilot gas valve open on the oven control.
This is also often found in very old furnace systems and is called a "millivolt" system where the thermocouple was not only used for the pilot light but the thermostat circuit.
So, a thermocouple is housed in a metal probe, takes a few minutes to get enough heat into the junctions to keep the gas valve open, it also takes some time for the probe to cool down enough that it no longer generates enough voltage to hold the valve open.
Your experiment actually would be better if you simply wait a few minutes.. to allow the thermocouple to cool. Turning it off then back on immediately after flame has extinguished is not a valid test.
However, keeping in mind that while the gas pressure will drop to a point that there is not enough to sustain the pilot.. The thermocouple will hold the gas valve open a short time after no more flame and allow whatever small amount of propane left in the line still flowing. This will not be enough propane to be a hazard but you will still be able to smell it for a short time.
