Soot from Atwood water heater pilot light

[nickcrowhurst]

There's always some little issue with our trailer when I get back to it after abandoning it for 8 months in FL, and this year was no exception.
The water heater started and ran perfectly, with a good blue flame, but the pilot light was yellow, large, and lazy. After a day there was enough soot build-up to fill a teaspoon. This cool flame was insufficiently hot to quieten the automatic re-lighter, and this was sparking constantly.
On the front of the gas valve is a screw marked "pilot adjust", but when I removed the Torx screw, as instructed in the manual, there was no adjuster screw underneath. I searched this forum, but could find no mention of this precise issue. A Google search revealed one suggestion that a dirty main burner tube could upset the air flows and cause the yellow pilot; however, I had dismantled and cleaned the main burner tube. The Google search also revealed on the Atwood site that "no attempt should be made to adjust the pilot flame."
I therefore again dismantled the main burner and pilot assembly for inspection. I noticed that the pilot light tube was constructed as a Bunsen Burner, with a small fixed size air hole in the side of the pilot tube. This hole was normally concealed from view. I deduced that if this hole was partially blocked, then the symptoms would be as described. I could see no blockage, but the tube is narrow, and the partial flap at the flame end makes it difficult to inspect. I therefore dismantled the pilot tube using a wrench, and laid the tube on the bench for inspection. I used a wooden toothpick to slide down the tube to clean it, and then blew down it from both ends.
I reassembled the pilot and burner tube. The water heater pilot is now blue, the automatic re-lighter is content, and so am I. I suspect this problem has been gradually building up for a few years. I report this isssue in case there are others with soot building up from an air-starved pilot light.
Nick.

[CanoeStream]

Hi Nick. Did you look in the air inlet for a spider web? I watched Jack do this fix last June. That was a very sooty problem until he cleaned it out. There's not much room and it takes a very small box wrench to reassemble.

Let us know ... but then you would!

[lewster]

Nice job Nick!

You did a fine job with your oxygen starved diagnosis, and you method of cleaning the pilot delivery tube was spot-on. Good on ya!

[CanoeStream]

I can tell I was in a hurry this morning... Should have known better with Nick. He's an excellent sleuth!

[nickcrowhurst]

[quote=CanoeStream]Hi Nick. Did you look in the air inlet for a spider web? /quote]

Bob, I suspect you are right about a web in the small pilot tube. Whatever was causing it was invisible, and very small. I wish I could share some of this heat with you. My son tells me it was 4 degrees your way yesterday, and I'm sheltering from 81 in a public library with AC here in FL. Lewster, thank you. you are too kind, as ever.
Nick.