suburban lp furnace fan not coming on?

[mrd341]

hello all! While checking out the gas furnace on my "new to me" 2003 winnebago adventurer 35u, i slid the thermostat over to the gas setting and heard the burner ignite and stay on, but i noticed that, although the furnace was working and warming up the rv, there was very little air coming out of the floor vents, like heat was coming out but the fan was not coming on. does anyone know if there is a blower fuse or switch that i could check before opening the unit up from the outside rear of the coach? thank's for any help
dennis

 

[darsben]

If the burner stayed lit then likely it is NOT the blower motor. The sequence of operation usually has the blower motor coming on first and closing a sail switch. The closure of the sail switch allows the gas valve to open thereby producing heat. So first I would check all heating runs to make sure none of the flexible ducting has come loose.

If nothing is found then I would wonder if the sail switch is stuck in the closed position allowing the heat to come on even though the fan not working

 

[mrd341]

thanks for the response, you are correct, i had the chance to check it again and i definitely heard the fan kick on and it appears to be working properly. i think it was just blowing a little less than i thought it should when i looked at the diagram of the heater and saw what looked like a pretty good sized blower! lol, thank's again!

 

[grashley]

Just because this was explained does not necessarily mean there is no problem.  Ducts can pull loose from their connections.  Manufacturers use flex duct pipes, and they are subject to poor routing, kinks, collapsed ducts, dust collection and other issues that can affect air flow.

You have gotten past the first hurdle, but you may wish to continue checking things.

 

[Gary RV_Wizard]

Grashley is right on target - duct air flow problems are quite common.

 

[mrd341]

thank's for the info, i was mainly concerned with the possibility of the fan motor being bad at the time because i had previously discovered that the notorious  coach heater fan is making a horrendous sound when the switch on the dash is turned on! the previous owner had pulled the fuse and i did not know what it was for until i did some research on it recently, looks like a real doozy to fix, especially after having to reset the limiter switch on the rear of the hot water tank the other day, i invented some new words during that experience!lol learning a lot though!
are the ducts from the heater accessible to check somehow?

 

[Gary RV_Wizard]

The heat ducts are usually accessible at either end, but in-between is anybody's guess. They may run behind cabinets, under the floor, etc. If you have the common flex ducting, they simply attach to ports in the furnace side/back, so pull off whatever panels cover the furnace and see what you can see.  They are merely clamped over the outlet port, if you can get your hand in there.  Access will vary for different floor plans, so we can only guess.  The outlets in the walls or floor are removable as well, but just how depends on the make of the outlet. Usually just some screws.

 

[mrd341]

ok, thank's, i will try and trace them today and see what i can find, i know that the furnace is not accessible from inside the coach and has to accessed from the outside rear on this adventurer by removing the inlet/outlet vent panel

 

[PancakeBill]

Not sure about your year, but on my 2000 37G  the duct runs fore and aft and have seen no flex doses.  Might be some, but they are not apparent like in my Southwind.  There conceivably could be some blockage, but you could probably run a snake from one end to the other and get a duster or something to check. 

I notice there is not a ton of air coming through.