Does my thermople just need cleaning? Do these Majestic DV360 flames look OK?

[Highschoolhank]

I have a 20 year old Majestic DV360 natural gas fireplace. In place of an on/off wall switch I use a furnace thermostat.

Over time it seems that once the pilot is lit and the Honeywell gas valve is turned to the on position, it's been taking longer and longer (on the order of several minutes now) for the burner to ignite once the thermostat is turned to heat with the set point above the room temperature. I can hear the thermostat click as the contacts close.

I did some testing of the thermopile output once the gas valve was in the on position and it appears that it is slow in getting to the 325mV output necessary to operate. Does this indicate the thermopile is on the way out or that it might just need cleaning?

In working on this problem I saw a couple flame-related things that I would like some opinions on. One is with the pilot and the other with the burner flame.

With the pilot I'm concerned about the flame that can be seen in that narrow slit next to the thermopile. It looks like it is underneath the "platform" that the thermopile, thermocouple, etc. sit on. Is that OK or is there gas leaking where it shouldn't be?

With burner I expected the flame to kind of uniform be all across the width whereas it appears to be just in certain dintinct spots. Is this pattern normal?

Thanks for any input!

 

[Lennox65]

I have a 20 year old Majestic DV360 natural gas fireplace. In place of an on/off wall switch I use a furnace thermostat.

Over time it seems that once the pilot is lit and the Honeywell gas valve is turned to the on position, it's been taking longer and longer (on the order of several minutes now) for the burner to ignite once the thermostat is turned to heat with the set point above the room temperature. I can hear the thermostat click as the contacts close.

I did some testing of the thermopile output once the gas valve was in the on position and it appears that it is slow in getting to the 325mV output necessary to operate. Does this indicate the thermopile is on the way out or that it might just need cleaning?

In working on this problem I saw a couple flame-related things that I would like some opinions on. One is with the pilot and the other with the burner flame.

With the pilot I'm concerned about the flame that can be seen in that narrow slit next to the thermopile. It looks like it is underneath the "platform" that the thermopile, thermocouple, etc. sit on. Is that OK or is there gas leaking where it shouldn't be?

With burner I expected the flame to kind of uniform be all across the width whereas it appears to be just in certain dintinct spots. Is this pattern normal?

Thanks for any input!

View attachment 302233 View attachment 302234

That pilot flame looks "lazy". It is barely touching the thermopile when it should be fully engulfing it.
Cleaning the pilot will definitely help with that. The burner flames are designed to come up in certain areas.
When the logs are placed properly, the bigger flames will be visible in the spaces between the logs.

 

[Highschoolhank]

That pilot flame looks "lazy". It is barely touching the thermopile when it should be fully engulfing it.
Cleaning the pilot will definitely help with that. The burner flames are designed to come up in certain areas.
When the logs are placed properly, the bigger flames will be visible in the spaces between the logs.

Thanks! I see what you mean about the flame not engulfing the thermopile. I have a small tapered brush, nylon I think. Is it ok to clean the pilot light holes with it?

 

[Lennox65]

Thanks! I see what you mean about the flame not engulfing the thermopile. I have a small tapered brush, nylon I think. Is it ok to clean the pilot light holes with it?

That probably wouldn't help much. It is the pilot orifice that needs to be cleaned and that is screwed in below the pilot hood.
If you look straight down in your first picture you will see a thin metal retaining clip.
Just pry one side of that clip out slightly and you should be able to just lift the pilot hood off. (Do this when the pilot is off and cool of course) The orifice is threaded into the pilot tube, I cant remember (If I ever even knew) the size but it is a standard Allen Wrench.
Unthread the orifice and take it out. Use compressed air to blow out the orifice, the pilot tube, and the pilot hood.
Reassemble everything and you should be good to go.

 

[Highschoolhank]

I got the clip off one side (see pic) but the hood still seems firmly attached. I found this video showing the hood removal (

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) so I can see what is supposed to happen, and in the video the clip is still completely in place. So I presume the hood is just stuck probably never having been removed in 20 years. Is it safe to use pliers to gently try to wiggle the hood, or a screwdrive to gently lever it up? What about using any kind of lubricant?

Thanks again for all you advice!

 

[Lennox65]

I got the clip off one side (see pic) but the hood still seems firmly attached. I found this video showing the hood removal (

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) so I can see what is supposed to happen, and in the video the clip is still completely in place. So I presume the hood is just stuck probably never having been removed in 20 years. Is it safe to use pliers to gently try to wiggle the hood, or a screwdrive to gently lever it up? What about using any kind of lubricant?

Thanks again for all you advice!

View attachment 302548

You can try to pry it up but they made two types of pilot assemblies, the one that you can remove the top and one that the top is permanently fixed. By some cruel coincidence, they put the retaining clips on both models, even though it serves absolutely no function on the one that is not convertible. If yours is the latter, then it would be considerably more difficult to access the pilot orifice.
It would involve removing the burner tray and loosening the fitting on the pilot tube.
You can try blowing compressed air into one of the three openings on the pilot hood and see if that helps before digging deeper.

 

[Highschoolhank]

It appears there is a seam between the hood and the pilot body. Do you know if the 1 piece assembly had a fake seam (like it had a non functional clip)?

 

[Lennox65]

It appears there is a seam between the hood and the pilot body. Do you know if the 1 piece assembly had a fake seam (like it had a non functional clip)?

I don't know. When I could not remove the top, I just replaced the entire pilot assembly. Do you have the manual that came with the fireplace? If you can find the part number for the pilot assembly, you will be able to better research it.

 

[Highschoolhank]

Ok, thanks! I think I've had it. After tapping on that seam and making no progress, when I lit the pilot it was practically non existent. Used some compressed air to blow through the hood and things got better but not sure I'm back to where I was to start with. Need this working reliably by Thanksgiving so may have to get a pro in, assuming I can get one at this time of year. Thanks again for all your help.

 

[Highschoolhank]

One other question if I may. When I had things somewhat apart it appeared there was a hole in the pilot assembly under where it is mounted (similar to what is in the attached pic) that I presume is for air intake. If I can blow compressed air into that hole might that help clear the orifice?

 

[Lennox65]

One other question if I may. When I had things somewhat apart it appeared there was a hole in the pilot assembly under where it is mounted (similar to what is in the attached pic) that I presume is for air intake. If I can blow compressed air into that hole might that help clear the orifice?

View attachment 303334

Yes

 

[chrisarrington]

I'm with Lennox. Replace the pilot assembly. I have soaked them down with PB Blaster and everything else imaginable. The way that piece is made, once it rusts together, I replace the whole thing. That does look like a flame underneath the assembly and is evidence the orifice is clogged somewhat.