RV furnace

[Frances DeHart]

It will be hot for a 20mins then it just blows cold air I have shutt it off and turned back on that seemed to work but it still keeps blowing cold air can I get some suggestion?pretty please!!
1977rockwood thank you in advance!

[Lakota Wolf]

Sounds like a problem I had a while back,,,, Make sure your regulator is working properly,,,If the pressure drops,, it will kick the furnace off,(excluding the motor).My regulator was approx a year old and it bit the dust,, it happens. ALSO,, check for Mud wasps nest and debri.  I took my furnace completely out and cleaned it all out,, had a few hidden dauber nests inside the burner tube. You Tube has a few video's of what others have done and show what they have cleaned out of their furnaces.. And YES, Mud daubers can and will sneak through the screen and build a condo complex inside the furnace tube. Whats funny is,, during spring and summer,, they can build a nest in a matter of a few days,, And with furnaces, it dont take much to throw them outta wack.   Good luck,, keep us posted what you find.

[Daniel Long]

Thermocouple is my guess if you have enough LP gas pressure to the line. A lot of those are the 12v furnaces by Suburban that need about 11 lbs of pressure to operate. The termocouple going bad would cause the pilot to go out and stop the heater portion.

Found this to be one of the better suppliers with diagrams and such. I have a Suburban NT24M I'm working on now.

http://www.pplmotorhomes.com/parts/rv-furnaces/rv-furnace-parts-ins...

[Frances DeHart]

I will definitely check that out Daniel I plan on pulling it out this summer and cleaning it and everything

[david craft]

Make and model of the furnace is a good start. Make sure none of the vents are obstructed, you may be short cycling the high temp limit. You can run it with the interior door panel off exposing the heat element, that would let you know. Don't do this with dometic 900/901 series furnace. If LP tank was overfilled, you could be freezing the reg evidenced by frost on the reg. Low lp level could be preventing the liquid from vaporizing but that would be in severe cold. You want 11 water column inches or a little less than .5 lbs pressure on the gas.

[Frances DeHart]

Hi David I am hoping to be able to get the make and sell of the furnace tomorrow right now the way it is parked I can't get close enough to really see anything from the outside. I didn't find I put a new tank on it with a hose one end had a bigger hole in it then the other end going into the tank and that seemed to make a difference I haven't had a problem with it.i will have more information as tomorrow we are going to mow it so we can start brake work on her! Thank you for the great information!

[david craft]

The ductwork I was referring to was the interior heater ducts. Either in floor or walls that may be cover with carpet or ?

[Tina]

Just FYI  and something to look for on this subject, David Craft hit on a good point to look for.

While I was doing the tear out of all the bad stuff in a water damaged unit, I happened to look under the couch/pull out bed.  The heater duct from the furnace to the register vent had been almost completely crushed closed.by the couch frame that was sitting on it.  It was probably only allowing 20% airflow through it.  Also the register vent, located at the front and under the couch was partially blocked by some eons old shag carpeting.

It's hard to believe any heat got through this RV at all. LOL

[Frances DeHart]

Thanks guys I'm definitely going to get this taken care of this summer before fall as I am living in her they the winter. Tina great information I'm gonna check that out too.