Quieting the Suburban furnace model NT-16SE, same as the NT-20SE - Page 9 - Fiberglass RV


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Old 05-18-2013, 08:18 PM   #113
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Yes the OP replaced it with an Atwood 8912-2
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Old 05-19-2013, 01:02 AM   #114
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Thanks, Steve. I'll check this model out. I am also going to check the motor bearings as they might be part of the problem.
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Old 05-19-2013, 06:57 AM   #115
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Quote:
Originally Posted by Steve Hammel View Post
Yes the OP replaced it with an Atwood 8912-2
I believe that is the Atwood Everest "8012" model, the one I have in my unit, lowest 12v draw currently offered.
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Old 05-19-2013, 08:22 AM   #116
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Originally Posted by cpaharley2008 View Post
I believe that is the Atwood Everest "8012" model, the one I have in my unit, lowest 12v draw currently offered.
Yes it is I pressed the 9 instead of the 0.
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Old 10-22-2013, 08:35 PM   #117
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My method for quieting the Suburban furnace

I too was hoping to see some tips here on how to quiet my Suburban furnace, but the messages took a different tack and never quite got there. So I had to figure out a way to do it since the noises were driving me nuts. This is what I did recently and ended up very happy with the results.

I bought my 1983 Scamp about 6 years ago and the first time I used the furnace it made noises. Later, I bought a used replacement unit since something had to be better than that one. It was, but still had some noises. Earlier this year I took it out and wanted to fix the noises. After removing the heating unit from the housing and tested it using the pickup battery. Funny thing, the motor sounded fine, that was not the cause of the noises. I found the noise was not caused by a bad motor, bent fins, dry bearings, etc, even though it sure sounded like it.

With further investigation, I found there are no screws or anything securing the heating unit frame on the backside of the heating unit to the housing. This allows it to vibrate inside of the housing when running, thus producing the sounds, among other things. I reduced the noise a lot by bending the sides of the housing away from the heating unit by inserting a screwdriver and twist it on each side of the housing to hold the housing away from the rear frame of the heating unit. That worked for a while, but by the end of summer, some noises returned and were irritating me again.

I decided this time I would track down every shiny spot on it from rubbing against other metal, and isolate the source of the screeching sounds if it meant taking it apart down to its last nut and bolt.

I have kept the old original furnace as a "parts" furnace in case I needed some parts from it in the future. Before taking the current one out, I decided to check every point on the old one for signs of rubbing that was causing the screeching noise when it ran. I wanted to see if I could get some clues there also to help when examining the current one.

After removing the old heating unit from the outside housing I wanted to isolate the specific cause so I checked everything that moved one at a time. What I found was numerous contact points that were causing the noises, and a real surprise regarding the exhaust tube. The photos show the areas of metal I found that were bright and shiny and rubbing against other sheet metal.

I checked the closeness of the exhaust tube to the hole it passes through in a support piece. I found not only shiny spots on the tube when I wiggled it, but a crack in the tube where it connects to the heating chamber!! Now just what is that doing there?? After taking the photo, I twisted the tube and it didn’t take much for it to fully break off. (see photos. Put cursor over photo for a description of what it is showing)

The guy I bought it from said his dad used it for a while. I didn’t ask what his dad died from. Hope it wasn’t asphyxiation.

So then I was ready to remove the current furnace again. Below are the steps taken to remove it and isolate the squeaks and screeches and eliminate them. It is not a difficult, scary or dirty process. Just take your time and it will turn out fine. It will be some of the best hour or so you have spent with your camper when done.
 
To remove the furnace from the camper:

Disconnect the battery. 12 volt power is going to the furnace and to the thermostat. Make sure gas is turned off at the tank.

Remove the two screws and front panel on the furnace

Remove the screw (s) along the bottom front of the furnace that hold the furnace into the cabinet space

Reach back along the side and disconnect the 4 wires leading into the side of the furnace. If you didn’t already disconnect the battery, you will find out why when you disconnect the wires. They are still hot and those sparks tend to really surprise the snot out of you if you touch something or they touch the circuit board

Use ¾" wrench and Channel Lok pliers to loosen the gas connection. Then should be able to remove the rest of the way with your fingers

Pull the furnace forward and it will come right out of the space.
 
To identify the cause of the noises:

Remove the two screws on the front side and bottom that have a label next to them that says "Don’t’ remove these screws except to service unit". You can then pull and push the heating unit out from the housing.

When pulling it out, be sure to feed the wires on the side into the hole so they don’t get caught. You now will have a very good view of things.

Check every inch of the heating unit to find any shiny spots resulting from metal rubbing against metal. I have included some photos of those areas where I found some of the problem areas.

The piece of metal that holds the sail switch had shiny areas that showed it was rubbing against the side of the housing on both the old one and the current furnace. (See photo) That piece is just too close to the housing and causes noises. Also, bend the two tabs at the front of the metal plate away from the heater. Check that the sail moves freely.

Do the same for any other metal that vibrates against other pieces of metal. (see other photos). And no, the exhaust pipe showed no damage or cracking at all on the current furnace.

I wanted to specifically check the motor, so I opened the pickup hood, set the heating unit on the motor and connected it to the battery. I twisted the two blue wires that go to the thermostat together, and then connected the hot and ground to the pickup battery. It takes a few seconds for the motor to start as there must be some kind of delay switch or something. Funny thing, the motor sounded fairly fine, but there was a little whistling.

I removed the back intake housing (see photo) and found a mess of sand that fell out and more when I stood the heater up and shook it some more. The intake fan sucks in anything that is in the air, including sand since there is no air filter. No wonder it is so dirty. That gives you access to the squirrel fan on the back of the motor, as well as the blades on the front of the motor.

I ran the motor again and thought the sound was coming from the squirrel fan. I removed the squirrel fan (you will need two different sizes of small, long shank alan wrenches to get them off) and cleaned the dirt and varnish from old oil off it with a soaking in a strong cleaner, using an old tooth brush, and Q-tip, including between the individual fins. I also removed the front fan blade and the motor and cleaned that also, and put some oil in each bearing even though it says it is permanently sealed. Like chicken soup for a cold, it may not help, but it can’t hurt

When both fan blades were still off, I ran the motor again and it was super quiet. It confirmed my suspicion the problem was not bad bearings in the motor. After assembling the blades and testing it again, it sounded just like it should.

When done checking everything, slide the heater back into the housing. Feed the other four wires back out of the side hole when inserting the heating unit back into the housing.

Be sure that the metallic tape on the front side that covers a large hole is good. ( see photo) If it is not, hot air from the furnace will escape and heat the area under the sink instead of directing it out the front of the furnace.

Replace the two "Do not remove screws" in the front and you are ready to place the furnace back into the camper.

However, before that, I drilled and put a sheet metal screw on the top, bottom and right side of the housing that screwed into the rear heating unit square frame. (see photo) There isn’t much there to screw into, but just keep drilling a few holes until you hit it. There isn’t anything around it to damage. I didn’t put one on the left side as I didn’t want to accidentally interfere with the movement of the sail switch.

To re-install in the camper:

Line up the furnace and start to slide it back in. Keep the two wires that go to the thermostat to the left side so they don’t get hooked by the furnace when sliding it back.

When it hits the pipes, you then need to reach back and line up the top pipe at the back of the furnace with the top tube coming from the outside of the Scamp. You just need to line up the top one as the other will line up automatically. When lined up, finish pushing the furnace back as far as it will go.

Reconnect the four wires and the gas line. Make sure the gas connections are tightened very hard.

Turn the gas back on at the tank. Check for gas leaks at the connection by using some soapy water to see if any bubbles are produced. If not, then the connection is tight. If you see bubbles, tighten the connection some more.

Light a burner on the stove to remove some of the air that is in the gas line and makes it easier to light the furnace.

Turn on the furnace at the thermostat and notice the huge difference in what it sounds like when running. No more screeching, just the strong force of air from the fan!

Now I know what it sounded like when it was new. If you do not hear the electrodes click, turn the thermostat off and wait for 15 minutes for the furnace to cycle and be ready to fire. Then try again. It should click and ignite.

Replace the screw securing the furnace to the cabinet and replace the front panel. You are done. I hope this helped solve the mystery sounds coming from your furnace.

I believe the biggest cause of the screeching was the squirrel fan, the metal plate holding the sail switch rubbing against the housing, and the rear part of the heater vibrating inside the housing.
 
Attached Thumbnails
1 - Shiny area on exhaust pipe.jpg   2 - Shiny spot on outside of sail switch plate that rubs against housing.jpg  

3 - Shiny area on rear heater frame.jpg   4 - Shiny sopt caused by sail switch against inside of plate.jpg  

5 - Crack in exhaust pipe.jpg   6 - Broken exhaust pipe.jpg  

7 - Rail inside housing. I bent it at the rear to keep it from vibrating against the heater.jpg   8 - Sheet metal screws I put into rear heater frame.jpg  

9 - Keep hole covered with the metalic tape.jpg   10 - Air intake pipe. Remove screws and see what all falls out.jpg  

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Old 10-22-2013, 08:44 PM   #118
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excellent write up
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Old 10-25-2013, 09:34 PM   #119
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Thanks, Jim. Great write-up and I am looking forward to tearing mine apart. Just drove down from Alaska with mine and could hardly stand the furnace noise!
ron.
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Old 11-07-2013, 11:20 AM   #120
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Additional information

I go into greater detail about the cracked and broken exhaust pipe, and preventive steps I took to avoid the problem in the future, in the thread: "Cracked furnace exhaust pipe" in the Forum: "Problem Solving: Owners Helping Owners"

Also, I posted this message about fixing the furnace noise in a thread: "Fixing noisy Suburban furnace" in this Forum. It is just a little down from this thread. It is a repeat with very minor edits as the message here. So if you read this one, you don’t need to read the other one.

Scamper Jim
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Old 06-04-2014, 12:44 PM   #121
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I know this thread is ancient. But I know many people have trouble with these units. I have fixed about a half dozen of these. Several of them just in the campsite as the problem popped up in conversation around the fire.
Its the electric motor bearings in 99% of the cases.
Of course you should take it to a qualified repair person and I am in no way suggesting one should do the repair.
I fully disassemble the unit to and pull the electric motor apart. Pop the rubber seals off the bearings with a pin-vise and pack with some new SRI or similar grease. Solved.
Yes there is a bit of dis-assembly. I can do the whole job now in about 30 minutes after some practice.
I have A LOT of experience with bearings and it really surprises me how much noise is amplified and resonates from the case when the bearings start getting low on lube.
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Old 06-04-2014, 02:38 PM   #122
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Ergo,
The squeaky wheel gets the grease - Wikipedia, the free encyclopedia
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Old 08-17-2014, 12:51 PM   #123
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It sure looks like switching over to an Atwood Everest 8012 II if your Suburban NT-12 E wears out..... Looks like a fairly simple swap but i would imagine the outside air intake and exhaust would be different and require a different hole cutout
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Old 09-20-2014, 02:31 PM   #124
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Hi Scamper Jim and all,

I had saved your write up for future reference and today I got to use it. We just returned from a trip and with colder weather had several mornings where we used our Suburban heater. It vibrated and squealed until it warmed up and then sounded normal.

Now that we're home I took it apart following your details and was able to eliminate the noise. I also heard some sand and removed the back intake housing and found a mud dauber nest. I had installed the mesh covers over my vents but suspect this nest is from the time with the PO.

Thanks for the detailed write up. It works!
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Old 09-21-2014, 11:56 AM   #125
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Hi Ken,

It is nice to hear of your experience with my description of the repair process. You are the first to provide feedback of their results even though there have been about 8,000 views of the thread since my original posting.

I figure: 1) some never got as far as my post at the end of the thread, 2) decided to put up with the noise, 3) installed a different heater, 4) were waiting for others such as yourself to do it and see if it is worth the effort, 4) had someone else do the work after seeing the steps and getting dizzy.

As you found out for yourself, it in not a major project as those furnaces were made so they can actually be worked on without having electrical and mechanical engineering degrees.

Just yesterday I returned from a 4-day trip to southwest Colorado area from Denver to Lake City, Pagosa Springs, Durango, Silverton, Ouray, etc. and back home The fall colors of the aspens in the high country were spectacular.

I found out something real interesting on the trip. I don’t know if it applies in others areas or states, but some of the national park campgrounds are still open and are free. No camp hosts, water or trash available, but free. These are regular campsites, not just dispersed camping. One of them is the Silver Thread campground about 20 miles north of Creed. I checked with the ranger station in Creed and sure enough, in fact it stays open year-round, closed only if due to heavy snow. Another campsite at Cimmaron, CO is still open and even has a camp host..

Ergo, it would seem that some of the best camping is after the cg’s officially close the weekend after Labor Day, and then check to see which ones are still open to catch the fall colors. Very little traffic during the week and you practically have the campground and roads to yourself. Be sure you have a good furnace in your camper when in the high country around 9,000 feet that time of year.
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Old 11-25-2014, 10:10 PM   #126
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question... I am new here so hello,

I just bought my camper and the furnace is not currently working... no noisy fan here, mine is apparently seized. So should the fan assembly spin freely with no power to it much like a ceiling fan? or is that my problem?

thanks for any helpful thoughts in advance
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