Suburban furnace problems

[Herk7769]

I was leaning toward bad motor too. If it runs intermittently, it should smell (some) from the insulation overheating though...

[The_Stuff]

I wish the furnace had a blower option... would make distributing heat very easy..

[popbreed]

My working career was in DC motor manufacturing and problem which can occur and is difficult to isolate is a poor commutator connection on 1 bar of the comm. Motor runs but does not have full performance (motor may perform within manufacturing tolerance) but starts fine until it stops on the open bar. Then it will not start unless someone or something moves the armature. Even worse, the connection can test good when originally manufactured but then goes bad (open) over time (oxidation of the copper). Typically these connections are made with a fusion process which is done with heat and pressure which must burn back the enamel insulation on the wire and crimp the wire and produce a good electrical and mechanical connection. You could try moving the armature (blower impeller) slightly when the blower will not start and try it again.

[grandpaofthree]

I am sitting here laughing about how far over my head these replies are. I have a friend with a lot more knowledge than I, so I will seek his help now that I have some direction. Right now, the furnace is operating at what I know as "normal" when connected to the car...the blower blows full blast, the heat is strong, etc. My understanding of the sail switch is that if the blower does not fully engage, the sail switch will not call for ignition of the gas. Right now, all of that is happening.

Thanks for all of the replies. All great info!

[buckisland1950]

Took delivery of my new TT a 2011 Flagstaff classic superlite two weeks ago and everything was great. I checked the furnace operation specifically because last year I took delivery of a brand new 2010 ultralite and the first trip the furnace did not work. A circuit board turned out to be the problem. Well we took the Grandkids out for the weekend and guess what, the furnace didn't work. This time all I could hear was a relay click and then nothing. Dropped it at the RV place and received the news that the culprit is the fan. Hopefully they will have me back on the road tomorrow. I could not find a fuse labeled furnace and my thermostat has a fan auto hi/lo, on hi/lo which didn't do anything (of course now I know why). Just curious until I get my TT back does anyone have the same setup on the thermostat and does the on hi/lo setting control the furnace fan (fan selection on the ac/fan/heat/off switch does work for the ac unit).

[ArkyGeorgetown330TS]

I would think the hi/lo setting is only for the AC. The furnace has one speed, loud!

[grandpaofthree]

Buckisland1950,

When I covered my unit in October, the furnace was working intermittently. When it doesn't work, all you hear is a click when I turn it to heat on the thermostat. Based on what I have learned and some posts in a different thread, I am thinking that my problem is with a ground wire. When I get the "click" on battery or shore power, then plug in to the tow vehicle, the furnace then springs to life.

Hopefully your mechanic is right. In my case I have it in three times, each time it works for a while then quits.

Good luck
Ray

[caper]

I had the same problem. It was a dead spot on the motor com and the brushes were sticking. The service tech that worked on my furnace was pulling his hair out trying to find the problem. He would pull out the furnace and had it on the floor it would work. Put the unit back in and it would work for a day of two then stop working. Finally is would not work when he pulled it out. He took the unit back to the shop had it on the bench. When he moved the fan the furnce started up. The replaced the brushes and had the com. reworked the furnace has worked for over a month now. Hope you find the problem with your furnace soon. It hard to find a problem when it does not happen all the time.

[Dpatters]

Recently had our furnace Suburban furnace fail. Managed to get schematic from internet search. I took the mother board out and had it checked at a store. They said all was well. Ended up replacing the blower motor worth $200. Furnace worked well for a week and then began failing again. You could hear the motor relay clicking but there was no power getting to the motor. After inspecting the circuit board myself I discovered that the large connections of the relay contact were not properly soldered to the circuit board. This is a common problem on many electronic boards where the original solder job did not sufficiently heat the larger leads. Re-soldered the connection and all is well. I suspect the original motor was OK and that just my moving the board around first go around temporarily fixed the bad solder joint. Been running well for 2 weeks now.