HEATILATOR GNDC36 Fireplace - Need Help


I have a HEATILATOR GNDC36 Fireplace running on propane. I will try to describe it. It has a vertical stack to the roof ending with a terminator cap. It is a direct vent model, using room air, and has a standing pilot ignition. The gas control has the usual thermocouple and thermopile arrangement. The direct venting consists of a built-in fan that draws room air at the bottom, blowing the air upward behind the heating chamber and back out the top into the room, thus giving warm air. It has a plate glass removable front that pretty well seals the heating chamber from the room in the front at least. There are 2 separate wall controls to turn off/on the fireplace burner and the fireplace blower fan.
It is seven years old, and worked fine when I last used it two years ago. The current cold snap has caused me to want to use it again. I can't get it work right.
What happens is this. I ignite the pilot manually the usual way (turning the knob to pilot and while holding the knob in, pressing the igniter button which clicks a spark). I then turn the know to burner position, and turn the burner wall switch ON. After a slight delay the main burner comes on and will stay on. Now the bad part. If I close the front plate glass, the burner will not stay on - going out and taking the pilot with it. If I don't put the glass on, the burner will stay on, presumably forever. The blower fan seems to work fine off the wall switch - so I don't think that is a factor.
It is almost as if, the burner goes out from lack of air. So that raises a question. If I can't get any help as to what is wrong with my fireplace, I at least would like to understand where the air comes from to support the burner flames? I simply do not see any passageway(s). I have read and printed every web documentation on this fireplace, and no mention is made of where that air would come from.
Thinking that is my problem, I am looking to find out why air is not getting to my burners.
Anyone?
Thanks
Jethro
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Since my post, I bit the bullet and removed the imitation logs so I could better view the burner + pilot. Lo - I found the source of air that worried me so much. Turns out there are two elliptical holes under where the logs were through which the needed air would be supplied. That answered anyway. I have also vacuumed the insides including the pilot assembly. Also, as I watch the exposed burners now, I see that the pilot flame seems to deteriorate badly when I close the glass front panel. I think the down draft from the stack at the top is the source of that. I don't know what to do about that, but maybe I can move or raise the thermo duo so as to be more enveloped by the pilot flame. I have found no way to increase the pilot flame though. That surprises me. If there is an adjustment knob for the pilot flame, I sure don't see it.
At least, can you tell me how should I clean the thermocouple and thermopile? Maybe you have an idea about the pilot flame? Or moving the thermo pair?
Thanks again
Jethro
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I still am wondering how to 'clean' the thermocouple and thermopile. Also, I am thinking now that my pilot assemble is missing something called a 'pilot hood'. The diagram shows one, which I do not have. Perhaps if I had one, it would deflect the pilot flame more downward to better envelop the two electrodes. But, alas, as yet I cannot find a source to buy such a thing. Maybe I could make one?
Thanks
Jethro
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Have you checked the venting to your direct vent fireplace? Since you hadn't used it in a couple years, the vent and/or vent cap may be blocked by debris, bird nests, etc., which would definitely cause an oxygen problem and the fireplace going out when the glass is installed.
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On 9 Feb 2007 18:25:53 -0800, " snipped-for-privacy@yahoo.com"

No - and I thought of that. But is so cold and would require a trip up the roof to remove the terminal cap so I can look down the stack that this old man doesn't feel up to it. I certainly will have someone do that in the Spring.
Thanks
Jethro
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On 9 Feb 2007 18:25:53 -0800, " snipped-for-privacy@yahoo.com"

This is where I stand now.
I removed the imitation logs so I could watch the gas pilot and burner more closely. It looked to me as if the pilot flames were being drawn away by maybe a draft from the flue from the thermocouple & thermopile, and by so doing caused the thermos to cool to the point that the burner & pilot were shut off. This would seem to be a reasonable 'cause & effect'. At least to me.
I placed a small piece of aluminum foil so as to shield the pilot flame going to the thermocouple to in effect block this so-called draft a little. It did the job nicely. All day yesterday, the fireplace burned without a hitch. Turned it off - went to bed.
This AM, I fired it up, and again, the burner would not stay on, like before. On the theory that the draft was involved, I opened the glass panel on the front and lit the burner. It stayed lit, like it always did, as long as I kept the glass open. Again, on the theory that draft is involved, I let it burn for a few minutes to in effect heat the flue - and then closed the glass. That was hours ago, and it is still burning fine.
So, I wonder why this is happening now - whereas it never happen a few years ago when I was last using the fireplace. Maybe the flue is blocked a little by something. If it ever gets warm again, I or someone younger (of which there are many) should get up on the roof and open up the terminal cap for a look-see.
Thanks for your interest
Jethro
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