Majestic LP Direct vent shuts down

[mowildone]

I have a direct vent, installed in 95, that has developed a problem with not being about to maintain flame.
The pilot light stays on, burns blue, and is easy to relight. I would like to see more flame however. When the switch is closed to ignite the main burner, the flame will race down the tube, linger a short time and go out.
As this happens, the pilot flame gets smaller, all most to the point of going out. The flame stays low until the switch is opened, then it jumps back up. If the switch is closed right away, again, the burner flame just flashes. Let it rest a few minutes and the burner flames last longer again.

Checked voltage across TP and TH and TP. Just before throwing switch, with switch off for awhile, reads 450-500 MV. Switch thrown voltage drops to 150-200 MV, sometimes less and continues to drop.
That's it, I thought. The pilot light orfice is partially blocked. When the main tube comes on, the pressure drops and the partially clogged pilot orfice cannot maintain enough flame to keep the main valve open. Clean the orfice and solve the problem. I cleaned the pilot orfice and the thermogenerator. The main burner came on and burned as long as needed.
Worked for a week. Now we are back to the old problem. Could this be a LP tank regulator issue? We own the tank and it was placed about the time the fireplace was installed.
The only thing that has changed over time has been that we recently changed LP gas supplier. But the fireplace has worked fine for a month after he filled the tank.
I did not clean around the pilot tube. Also I am not able to adjust the pilot flame. If I turned the screw in, the flame got smaller but backing it out did not change its size.
Any thoughts? this is really bugging me.
One last question. The part numbers for this unit can not be found. Where can I get parts like a new thermogenerator?
Thanks for your help

 

[webbie]

I think you are on the right path - it sounds like a gas supply issue of some sort. The regulator, a kink in the line, the line too small, too long, etc.

As to the parts, you can probably determine them by the value type/number model, or the label on the unit. Woodmans has a LOT of replacement gas parts and can probably help if you get as much info as you can about the particular model and part.

See link to Woodmans at https://www.hearth.com/prod.html - bottom of page.

I have also found thermocouples at my local plumbing supply just by bringing the old ones in.....they are somewhat, but not totally, standard (at least on some models).