Pilot won't stay lit

[allison_1114]

I have a Day-Glo ventless natural gas wall heater that is only a year old.  The heater worked fine last winter, but this fall it isn't working right. 

When you light the pilot you have to hold down a knob for a few seconds to get it going and then you let up and select your temperature.  Well now you have to hold the knob down for a few minutes before it will ignite.  Once you get it ignited it will run until your selected temperature is reached and it will then shut off and the pilot will go out.  It has never done this before and I am clueless as to how to fix!?!?!?!

[hvacdrd]

Start by cleaning the pilot burner. A weak pilot flame will not produce enough heat to properly hold the pilot safety (thermocouple) - If cleaning the pilot does not help replace the thermocouple (this is the device the pilot flame hits)

[applianceman18007260692]

over the summer months a small amount of dust or web from a spider mite or a creature of simular species has partly blocked the ODS chamber located behind the pilot lite ,this is an easy, fix I use rust buster, to clean out the pilot, by inserting the end of the tubing of the rust buster, into the pilot light, and flushing out the pilot assembly, rust buster has a extended spout coming out of it for just such a task. after letting the rust buster dissolve, you then re-light the pilot assy ,you will notice that the flame is blue and about an inch or so long , this will help to maintain the flame over the t-couple and fix the problem, if I aint making sense, reply back ,and I will try to be more helpful. from what I know of these heaters, they have a compartment behind the pilot flame called an oxygen depletion system, as less oxygen is detected in the room, the flame becomes smaller and less heat to the safety magnet bulb releases the safety magnet, and shuts off the flow of gas usually just as the room gets warm. by flushing out the ODS chamber and gitting rid of this tiny obstruction the pilot flame will work properly.

[allison_1114]

You make perfect sense, I will have to try that, thanks for the help!!!!