Suburban Furnace issues

[RickB]

Hey all,

I brought this up a while back that I was getting a knocking sound in my SF 30 Suburban after it reached operating temp. I took it out today and found that there are two side to the squirrel cage fan assembly. one is the normal steel squirrel cage fan for distributing heat but on the air intake side there is a plastic (kinda flimsy) squirrel cage fan that appears to cool the motor and provide an intake air supply for the furnace. Well , I found a mud dauber nest in the plastic side that was a considerable mass ( about half your little finger) and that it was obviously making it spin out of balance. I cleaned it out, hooked it up to my battery charger and it spins just fine but there is no heat happening making things expand so I'm wondering should I use a hair blow dryer on the intake side to get the whole assembly warm? Do you think that would be a fair operating environment to see if the problem is fixed long term?

I would hate to find out that it is still not working correctly after I put it all back in.

Thanks,
Rick

Does anybody know what normal play with the squirrel cage assembly is?

[RickB]

I warmed it up indoors and used my blow dryer to get it pretty darn hot and it worked awesome. Hopefully it will work for many years I am sure grateful I am not spending a bunch of money on a new motor assembly.


Keeping my fingers crossed and planning on putting it back in tomorrow.

Anybody ever dealt with this before? Speak this evening or forever hold your peace.

Thanks,

Rick

[WEC4104]

Personally, I wouldn't put a lot of faith in the hair dryer approach.  You can try it easy enough, and if you still have the knocking sound, well, you still have a problem. On the other hand, if there is no knocking sound with the blow dryer,  it is not going to be conclusive.

I'd be interested in hearing if folks have performed "live" bench testing on Suburbans that have been removed.  Can these be hooked up to a gas grill propane tank using a standard regulator?  Naturally, it would have to be in a safe, ventilated area  (ie: outside).  Feed it 12 volts and simulate the thermostat closure?

[fe2_o3]

  Yes I've bench tested my Suburban furnace in my garage. 12 volts, Propane tank with regulator plumbed to furnace.  With a spare plug and harness I connected red to positive and black to negative. The two other wires when connected start the process as would the thermostat. Worked well and I set it on a TV tray in the door way to warm the garage for a couple of days...Cable

[redbus]

I would pull out the burner tube and clean it checking for burnout holes at the same time.I have seen mud dauber nests there also(really smells bad when burning out) then I will always bench test.

[JohnEd]

I bench tested mine and it worked really well.

For years my furnace worked like a champ.  Eventually I got a hold of a manual and read it thru.  I noted that the furnace is supposed to run on after the thermostat trips the furnace OFF.  I called the factory and they said that that was important to purge the furnace of unburned gas that would accumulate in the bottom of the furnace.  Sooooo out came the old thinking cap and a copy of the schematic and the multimeter.  I first noticed that the power in 12VDC wires were not properly labeled and also that the thermostat wires were much more stout than the furnace power wires.  Gave me pause and I wondered how stupid those guys were.  Then I noticed that the thermo wires were also not color coded correctly.  Finally I noticed that those stupid factory guys had actually switched the colors for the thermo and 12V power.  The next morning I was bright eyed and way more sober and I fingered it out.  I had run for years with the furnace being powered thru the thermostat lines and the dc lines were the thermostat function.  Crimey!  That was ten years ago and it is still working fine and in accord with the fact description.  Subs are tough built.

The coldest part of the entire furnace is the intake and distribution blowers.  One blower injests cold air from floor level and the other ingests cold air from OUTSIDE.  Say again why you are concerned with heating them?

Still luv ya,

John

[RickB]

John,

Although the intake is bringing in cold air the heater itself is still quite hot to the touch during operation. The idea I had of simulating operating temps was to get everything expanded up to operating temps. The thought being that something that didn't rub at start up may rub at full temp.

Update: The furnace is working awesome! ran it yesterday for over an hour and she purred like a kitten.

Sometimes we actually do win working on these things. The transmission fluid to Rotella 10/40 was a success earlier this summer, The short I found in the tailights that was causing my motor to shutdown, The complete rebuild of my cooling system!!! Hey this bus thing is getting easier. Great just as I start to get a grip on this thing...Winter approacheth. Darn it...

Have a great week,

Rick

[JohnEd]

Rick,

Glad to hear it is working "swimmingly".  They are a great unit. Mine is rated at 48KBTU if you can believe that.

The heated air plenum is the end nearest the inside of the coach and has all the ducts attached.  I am sure you are aware of that.  The end towards the wall, on mine, remains cool to the touch.  That is the air induction end.  I don't think it ever gets very warm as there is even a run-on period for the fan after the gas shuts off after a heat cycle.

My blowers set in to howling after the furnace ran for a minute or two.  really an unholy racket.  I oiled my motor bushings and it ran silent.....for a few weeks.  When the oil got the least tacky it set up a vibration and howl again.  I tore it down a few times and then ordered the new motor.  That solved the problem.  I am told to never oil or lube a steel to brass bushing and my experience seems to hold that true.

I also had my heat exchanger crack and let CO into the coach.  Wonder I am here as I "tried' to use the thing for  weeks till I gave up due to burning eyes and a foul taste and odor.  Got up a couple times at night to turn it off due to the smell.  Wonder it didn't kill me due to my insistence at least.  Get a CO detector and a propane detector.  When mine lights of with a whummp, my CO detector chirps once and I count that as a test.  It isn't supposed to whummp and I think that means I have a little to much gas pressure.  I solved that problem in the distant past by turning down the gas till it ran correctly and did not whummp at start up.  It is very subdued now but used to be a serious noise that you could feel in the floor thru your feet.  As I said, I should have died by my own hand long ago.  Drunks and Irishmen....Right?  I'm German/English/native Indian...go figure.

Be well,

John