Reply
 
Thread Tools Search this Thread Display Modes
 
Old 03-05-2011, 08:48 PM   #1
Site Team
 
azflycaster's Avatar
 
1975 25' Tradewind
Dewey , Arizona
Join Date: Mar 2005
Posts: 12,125
Images: 62
Blog Entries: 1
Furnace Noise

For the past two years when ever I ran the furnace (rarely) It sounded like the motor bushing were dry. The noise would start after a few minutes of operation and never stop. Today I pulled the furnace and ran it on a bench with no propane for an hour and it never made any noise at all. Could the heat from the furnace made any difference?

It is a Suburban NT-22A and the cross over tube is fine. I have a used NT-22 for parts that has a good motor in it (thanks Zep!) but it will take some work to swap out the motor since the blower assembly is different.

Any suggestions?
__________________

__________________

Richard

Wally Byam Airstream Club 7513
azflycaster is offline   Reply With Quote
Old 03-05-2011, 09:38 PM   #2
Well Preserved

 
1993 21' Sovereign
Colfax , North Carolina
Join Date: Jun 2003
Posts: 20,190
It may be the squirrel cage is barely touching the housing. The heat could possibly cause the metal parts to expand just enough to cause the noise.
It's more likely a dry bearing, but I've learned it's not always the likely that's the problem. It's also very possible your moving everything around to get it out of the trailer stopped whatever it was that was making noise.
__________________

__________________
overlander63 is offline   Reply With Quote
Old 03-06-2011, 07:59 AM   #3
Moderator
Commercial Member
 
eubank's Avatar
 
1967 30' Sovereign
Bosque Farms , New Mexico
Join Date: Jan 2004
Posts: 6,423
Humm. Leave the thing out of the AS and wait until a good, hot day in Phoenix. Put it in some enclosure (like an uninsulated garage) so that it gets too hot even to touch. Then run it.

Lynn
__________________
WBCCI 21043
eubank is offline   Reply With Quote
Old 03-06-2011, 08:27 AM   #4
Rivet Master
 
Lumatic's Avatar

 
1971 25' Tradewind
1993 34' Excella
Currently Looking...
Estancia , New Mexico
Join Date: Feb 2005
Posts: 6,642
Images: 16
Blog Entries: 1
My NT 30 screeches sometimes when the blower comes on. Sometimes a well placed kick will get it to run right again. I see 2 options replace the blower motor for a hundred and change or replace the whole furnace for about $350. So far I have not gotten around to pull it. What would you do?
__________________
Sail on silver girl. Sail on by. Your time has come to shine.
Lumatic is offline   Reply With Quote
Old 03-06-2011, 08:50 AM   #5
Slide Out Society #001
 
GCinSC2's Avatar
 
2007 30' Classic S/O
Somewhere , South Carolina
Join Date: Apr 2010
Posts: 2,051
Quote:
Originally Posted by azflycaster View Post
For the past two years when ever I ran the furnace (rarely) It sounded like the motor bushing were dry. The noise would start after a few minutes of operation and never stop.
Preface: I have never worked on one of these units.

.02$ info: If the unit has actual brass bushings rather than a ball bearing on the blower motor, brass bushings like oil, not grease. If you see a spot that looks like an OIL HERE hole, or if you see an oil wicking pad, try a few drops of light oil, 3in1 for example. Just don't use grease on a high speed bushing. If you have some old power hand tools, you might see the same on the ends. Brass bushings in need of lube chirp and I think you can really hear it at shut down when it is no longer powered, stops a bit abruptly.

If ball bearings, time for bearings.

Good luck.

Gary
__________________
S/OS #001
2005 Dodge Ram 2500 5.9L 6 Speed
16" Michelins, Hi Spec Wheels, Max Brake, Carslile Actuator, Equal-i-zer, Dill TPMS. Campfire cook.
GCinSC2 is offline   Reply With Quote
Old 03-06-2011, 08:57 AM   #6
Moderator
Commercial Member
 
eubank's Avatar
 
1967 30' Sovereign
Bosque Farms , New Mexico
Join Date: Jan 2004
Posts: 6,423
I put a new motor in our NT24 (I think) a few years ago. The motor had brass sleeves, not ball bearings.

But from the sound of Richard's, it doesn't quite sound like a bearing problem. When I've dealt with these before, they may start up with a screech, but as they heat up (practically overheat), some lubricant becomes more liquid, flows in, and stops the noise.


Lynn
__________________
WBCCI 21043
eubank is offline   Reply With Quote
Old 03-06-2011, 09:01 AM   #7
Rivet Master
 
Join Date: Dec 2002
Posts: 1,313
Images: 4
When the furnace is on the bench and running, it doesn't have to work against the back-pressure of the ducting and vents, thereby lesening the end loading on the bushes. When this occurred on my furnace, I dismantled the motor completely to gain access to the bushes, and a few drops of light oil cured your exact sysmptoms completely. I could not get oil to the bushes without total dismantling. Details of the work involved, and the tools required are detailed here:
http://www.airforums.com/forums/f427...ace-60957.html

Nick.
__________________
Nick Crowhurst, Excella 25 1988, Dodge Ram 2500 Cummins Diesel. England in summer, USA in winter.
"The price of freedom is eternal maintenance."
nickcrowhurst is offline   Reply With Quote
Old 03-06-2011, 09:21 AM   #8
Moderator
Commercial Member
 
eubank's Avatar
 
1967 30' Sovereign
Bosque Farms , New Mexico
Join Date: Jan 2004
Posts: 6,423
Good idea, Nick! Richard, when you do the bench test, plug the out-vents.

Lynn
__________________
WBCCI 21043
eubank is offline   Reply With Quote
Old 03-06-2011, 10:43 AM   #9
Rivet Master
 
Lumatic's Avatar

 
1971 25' Tradewind
1993 34' Excella
Currently Looking...
Estancia , New Mexico
Join Date: Feb 2005
Posts: 6,642
Images: 16
Blog Entries: 1
I think Suburban does not have any way to service the bushings/ bearings and the whole motor unit must be replaced. Do I have this right?
__________________
Sail on silver girl. Sail on by. Your time has come to shine.
Lumatic is offline   Reply With Quote
Old 03-06-2011, 11:24 AM   #10
Site Team
 
azflycaster's Avatar
 
1975 25' Tradewind
Dewey , Arizona
Join Date: Mar 2005
Posts: 12,125
Images: 62
Blog Entries: 1
Blocking the air flow did not change the symptoms, going to tear it down to get to the motor.
Attached Thumbnails
Click image for larger version

Name:	IMG_4917.jpg
Views:	92
Size:	249.8 KB
ID:	123774   Click image for larger version

Name:	IMG_4918.jpg
Views:	102
Size:	461.6 KB
ID:	123775  

Click image for larger version

Name:	IMG_4919.jpg
Views:	91
Size:	322.0 KB
ID:	123776  
__________________

Richard

Wally Byam Airstream Club 7513
azflycaster is offline   Reply With Quote
Old 03-06-2011, 11:54 AM   #11
Moderator
Commercial Member
 
eubank's Avatar
 
1967 30' Sovereign
Bosque Farms , New Mexico
Join Date: Jan 2004
Posts: 6,423
Quote:
Originally Posted by Lumatic View Post
I think Suburban does not have any way to service the bushings/ bearings and the whole motor unit must be replaced. Do I have this right?
I 'spect that you could probably get new bushings pushed in/on at a motor rebuild shop, but I generally go with a new motor if they're available and still fairly inexpensive. (Parts for the old tractor -- 1948 -- are rebuild-as-needed-purchase-if-absolutely-necessary, but Suburban furnaces are still petty common and easy to buy parts for.)


Lynn
__________________
WBCCI 21043
eubank is offline   Reply With Quote
Old 03-06-2011, 12:26 PM   #12
tpi
Rivet Master
 
2005 25' Safari
Trabuco Canyon , California
Join Date: Apr 2006
Posts: 866
Images: 2
I've had motors over the years without oiling ports where disassembly and oiling the bushings was completely successful. Some have had a felt type oil retainer. I just cleaned everything up and oiled them. On my house central AC the motor has run longer after I oiled it than it did originally before making noise.

OTOH if the motor is hard to get at, you may want to play it safe and just replace it.
__________________
tpi is offline   Reply With Quote
Old 03-06-2011, 12:36 PM   #13
Rivet Master
Airstream Dealer
 
Inland RV Center, In's Avatar
 
Corona , California
Join Date: Feb 2002
Posts: 16,499
Images: 1
Quote:
Originally Posted by azflycaster View Post
Blocking the air flow did not change the symptoms, going to tear it down to get to the motor.
Rich.

The motor can be disassembled so that you can easily lube the bearings, the source of the noise.

Or, sometimes you can stand the motor up on one end, and place the oil around the shaft. Repeat that a few times. However that only gets you to one bearing.

If the motor was run for many hours with the dry bearings, the bearings at this point, may be shot.

Replacement motors, however, are available.

Andy
__________________

__________________
Inland RV Center, In is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
cheap heat rv comfort systems - electric conversion of furnace? hshovic Furnaces, Heaters, Fireplaces & Air Conditioning 13 07-17-2012 02:18 PM
Need advice on furnace. SilverRanger Furnaces, Heaters, Fireplaces & Air Conditioning 5 05-28-2011 04:47 PM
A handy schematic snapshot from my furnace - 1970 Sovereign ranger_rick Furnaces, Heaters, Fireplaces & Air Conditioning 1 02-18-2011 11:34 PM
Furnace and Hot water heater complete Airdaddy Furnaces, Heaters, Fireplaces & Air Conditioning 3 02-02-2011 10:16 PM
Suburban Furnace Selection MDSilverado Furnaces, Heaters, Fireplaces & Air Conditioning 3 01-31-2011 10:40 AM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 12:09 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.