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Tom, HVAC Technician
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Experience:  16+yrs HVAC/R service. Residential Commerical Industrial
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We have a Monessen ventless gas log Model DEB30PM [new 2004]

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We have a Monessen ventless gas log Model DEB30PM [new 2004] (propane/LPG), manual control, that has been operational without problems for the past 5 years. The pilot light has been on continuously for approx. 2 months this season. We manually turn on/off the log flame using the control knob on a periodic basis over the course of a day, reverting back to pilot light when "off". Last night the pilot light went out on its own. Repeated attempts to relight it today have yielded same result, as stated in Troubleshooting section of our manual: "ODS/pilot lights, but flame goes out when control knob is released". Of the possible causes, the following have been ruled out: 1. Control knob not fully pressed in. 2. Control knob not pressed in long enough. 3. Manual shutoff value not fully open. We have since loosened dust & vacuumed vicinity of burner assembly, and used steel wool to "clean" the vertical metal pencil tip of burner. No change in results. What do you suggest next?

Hi, Tom here,


The verticle pencil tip you refer to, is it thin, aproximately 3/16" diameter or is it larger, aprox. 3/8" diameter?


And does it have a copper looking metal line from the probe to the gas valve or does it have a silver colored cable with wires to the gas valve?


Sorry, I don't know your exact system, but I think we can figure it out.


Let me know, Tom

Customer: replied 7 years ago.

Hi Tom, This is my 1st use of Just Answer, so bear with me.


Pencil tip is perhaps 1/16" black metallic, extending from a ceramic cylinder perhaps 3/16" in diameter. The feed line to the gas tube is silver (likely aluminum). The ignitor (ceramic cyl) has one black & one white wire leading to it. I can send a pdf photo to email address if that will help.



Thanks John,


I found a manual online and I think I know what you have. LP with manual control (no remote).


Observe the pilot flame while trying to light it, you need a good strong flame that contacts the thermocouple. If it doesn't get hot enough it will not produce enough voltage to hold the pilot valve open in the gas valve. It is generating a voltage of less than 1 volt to keep the pilot valve going, so it is critical for it to be a good flame.


Make sure it is burning strong out the end of the pilot burner, not a lazy flame that sort of curves up and barely touches the thermocouple. If that is the case, you need to clean the pilot burner first. (If it has never been cleaned it probably needs it anyway.)


With gas off, try using a small brush and some compressed air to clean any soot, dirt etc. from the pilot burner. (Look for the little tiny orifices down in the burner where the pilot gas comes out) .


After a good cleaning, try relighting the pilot and see if it holds in. If it does not, you probably need a new thermocouple. You should be able to pick one up at a hardware store or a stove/fireplace shop.


I don't know how accessible your pilot is, you may have to remove it to clean it good. Make sure the gas is off and when you reinstall, if you had to remove the pilot gas line, make sure the connection is tight.


If you are not comfortable doing any of these things, don't feel bad about getting a furnace guy out there to take a look at it.


Check the easy stuff first. Good luck with your fireplace. Hope this helps.

Let me know if you need further help.

Tom and other HVAC Specialists are ready to help you

No problem on your first time using Justanswer. I had the same feeling.


I looked at the Monessen manual again and the LP thermocouple is quite a bit different than one for natural so the chances of a hardware store having one is pretty slim. You may end up at a stove/fireplace shop to find one if cleaning the pilot doesn't fix the problem.


Monessen also has a website and I'm sure they could help you obtain a replacement.


Thank you for the accept. Much appreciated, good luck with your project.


Tom and other HVAC Specialists are ready to help you
Customer: replied 7 years ago.


Your response was helpful and confirmed my general approach re cleaning or potential inoperative thermocouple. I'll pursue cleaning further first. If no change, then replace the unit. Thanks.


Customer: replied 7 years ago.



Without removing anything more than the several imitation "logs pieces", I cleaned the gas tube with a pipe cleaner and observed significant fines (like powdered ash) falling from the silver cylinder opening about 3 inches from the end tube, and then blew out remaining dust. Upon reigniting the pilot light, the tip (approx 1/4" of the copper gas tube glowed bright orange, which had not occurred during the repeated prior attempts.

After waiting about 15 secs, upon releasing the spring loaded control knob, the pilot light remained "on" and the unit is now fully functional again.


Cleaning more frequently than every 5 years is clearly recommended. The pipe cleaner is now a fixture along the side of the hearth.


Thanks again. I posted two payments unknowingly, but have no desire to modify same, as your guidance gave me the confidence to proceed with repair on my own, resulting in successful resolution. I didn't think the thermocouple, nor the control valve, was the problem.



That is cool!! Glad you got it going. My journeyman when I got in the HVAC trade drilled into me....'Check the easy stuff first' and it has served me well over the years.


Thanks for the accept,, I didn't notice the double accept, but thank you.


Have a safe NewYears.



I will leave you positive feedback and appreciate the same when you have time.