Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 14, 2025 ...

hot water heater

November 10, 2014, 11:13:17 am

Hi,
Our '92 U300 just started leaving a black residue or soot above the vent and on the fiberglass about a foot above the hot water heater vent when using the hot water heater.  The hot water heater still works fine.  It has never done this before. 
Anyone have this problem before?
Thanks for any help with this,
Sue

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Re: hot water heater

Reply #1 – November 10, 2014, 12:38:45 pm

Maybe something is inside the vent and is burning (like a mud dauber)?

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Re: hot water heater

Reply #2 – November 10, 2014, 12:57:57 pm

Gas flames turn yellow and sooty when there is not enough air for complete combustion. Time to have it serviced.

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Re: hot water heater

Reply #3 – November 10, 2014, 02:41:35 pm

Yes, just pop off the cover and clean off the mud the little critters left there. Flame should be nice and blue. Any yellow in the flame means incomplete combustion and LOTS of CO (Carbon Monoxide). This is a super easy fix.

Pierce

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Re: hot water heater

Reply #4 – November 10, 2014, 07:20:44 pm

I had that happen when spider webs fouled the burner tube just down stream of the orifice. I cleaned out the burner tube, and adjusted for blue flame with as little noise as possible. All was good except for the burn stains on the painted portion of the water heater coverage. They faded, but I think the paint is scorched and can only be repaired with fresh paint.

You could also have nests (dauber, wasp, spider) in the flue. I cleaned the flue with a rag and a fish tape (for "fishing" electric wires). The flue can also be cleaned out with a strong stream of water. Try to keep water out of the bay and prepare to clean up a wet mess.

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Re: hot water heater

Reply #5 – November 10, 2014, 07:26:40 pm

Loosen the screw on the air adjustment flange and adjust it left or right until you get a good flame and loud rushing sound.

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Re: hot water heater

Reply #6 – November 10, 2014, 08:17:53 pm

The built in vacuum cleaner's hose is long enough to reach the water heater and the nozzle is skinny enough to fit into the combustion chamber if you take the burner out first. You can cut off an old piece of water hose and duct tape it into the vacuum cleaner nozzle to make an even skinnier, flexible nozzle that will go all the way through the combustion chamber and out the exhaust for a thorough cleaning. You can also clean your furnaces that way.

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Re: hot water heater

Reply #7 – November 10, 2014, 09:21:11 pm

Thanks for the suggestions.
We had already checked for foreign bodies and there were no mud daubers or nests, etc.
Will try try adjusting the air adjustment flange. 

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Re: hot water heater

Reply #8 – November 10, 2014, 09:50:59 pm

Always run a manometer test

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