# Pilot won't stay lit on Monessen  vent free fireplace insert



## alan1955 (Nov 28, 2017)

I have a 15 year old vent free Monessen DFX32NV that has worked flawlessly all these years but now I can't get the pilot to stay lit. It will ignite with the push button, but even after a minute of holding in the pilot switch it pops back out and pilot dies. 

I found someone else on the forum that had a similar problem and I did some testing based on that info. First off I want to make sure I understand the terminology. There are 2 wires coming from the large black rod on the igniter assy, which I believe is the ODS. When I measure across them, with a pilot flame, I get over 300mv. There is also a brown wire coming from a post that sticks up into the pilot flame and it goes to a fitting on the rear of the valve assy. If I measure between this and TH 3 on the terminal block I get about 130mv. 

I am somewhat confused about what each sensor does. I think the voltage from the brown lead keeps the gas valve open, as long as there is a pilot flame, and the ODS somehow detects a lack of sufficient oxygen and closes the valve. Based on the other post I believe I am getting correct voltages to the valve, but it's just not opening to allow the burner to come on. This leads me to believe the valve assy is probably defective, but I really don't want to invest over $200 if it is not. Any guidance is greatly appreciated.


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## DAKSY (Nov 28, 2017)

Look closely at the pilot nozzle. There is a small (1/16 - 3/32" Diameter) hole on it. Generally, it is on the back side.
That is your ODS. Make sure dust, pet dander or hair have not blocked the opening. Use a can of compressed air to clear it.


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## alan1955 (Nov 28, 2017)

DAKSY said:


> Look closely at the pilot nozzle. There is a small (1/16 - 3/32" Diameter) hole on it. Generally, it is on the back side.
> That is your ODS. Make sure dust, pet dander or hair have not blocked the opening. Use a can of compressed air to clear it.



I found what appears to be just an indentation, not a hole, on the back side of the gas nozzle. If I take a straight pin and try to poke through it, I just seem to hit metal, not debris. I can't imagine something that hard could be packed in there such that I couldn't run a pin through it.

I am almost at the point where I might just have the dealer I bought it from come out. They charge $99 for a cleaning, and if that doesn't fix it, it's $60 plus parts. Hate to spend that much if it's something simple but may have to bite the bullet.


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