richard5933

Suburban NT-32CD Furnace Blower Motor

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Trying to get our 1974 GMC Coach up and running. Got the LP system tested for leaks and safety issues, then tried to fire up our Suburban furnace. Things overall went okay, but it seems like the motor/blower is in need of help. The blower starts really slow, squeaks a bit, then eventually starts to blow air. On 120v it's okay once it gets going, but on 12v has trouble getting up to speed.

Anyone have experience either rehabbing the motor or replacing them? I assume that I'll have to pull the furnace to get to the blower & motor, but first I want to know if it's worth trying.

Thanks.

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wolfe10   

Might start by oiling the fan motor bushings (AKA sleeved bearings). Most hardware stores sell a light viscosity oil with long spout that makes accessing the shaft next to the motor easier.

If that doesn't do it, next step is motor replacement.

Also, make sure you do have 12+VDC (that your battery voltage is OK). If the fan spools up as it should when shore power is boosting battery voltage, but not on battery alone, be sure to verify battery condition and connections.

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Richard5933, It is always good to have a working furnace, especially in Wisconsin !

I have removed the blower motor(s) on the Atwood in our coach. Have not tried it on a Suburban  though. The blower covers have very little room and are sung with not much wiggle room to remover the outer portion of the blower cover. Had to remove mine because the Sail Switch had failed. The service center said that the furnace needed to be removed, but being a little on the stubborn side and adventurous side I decided to give it a go.  The hardest part was reinstalling the outer half of the blower cover. The trick I used was to use a sheet of Teflon placed on the bottom of the work area to make it much easier to slide the part into a tight space. 

Rich.

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I was actually able to get the furnace pulled without too much trouble or too many scraped knuckles. Luckily the floor of the wardrobe above the furnace was screwed in and acted as an access panel. The carpet in the wardrobe will need to be replaced, but otherwise things went well.

The inside of the furnace is actually pretty clean - looks like it was only used a time or two. All the paint is still on the heat exchange unit and other than a very stiff motor I can't really find a problem. On 120v it fired up and ran okay once the blower got to speed. It ran on 12v, but the motor really pulled hard on the batteries so I only did that for a brief time.

On a whim I called Suburban to see if they had a cross reference for a current motor which would fit our furnace. Believe it or not, they did. One is on order and will be here in a couple of days. Hopefully things will go together well and I'll be able to make this thing last at least another season or two. I'll try and post some photos as I do the motor replacement. The attached photo is of the empty cabinet where the furnace goes. Really glad I found the removable panel under the carpet.

tapatalk_1510005490513.jpeg

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That was my plan, but after doing some research it seemed that oiling the bearings would be a short-term solution. When I found that the motor was still available I decided to just order one and try for a longer-term solution.

Once I know that the new motor is in place and working, I'll probably try to open the original and see what could be done to repair it.

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1 hour ago, richard5933 said:

That was my plan, but after doing some research it seemed that oiling the bearings would be a short-term solution. When I found that the motor was still available I decided to just order one and try for a longer-term solution.

Once I know that the new motor is in place and working, I'll probably try to open the original and see what could be done to repair it.

No need to open the motor case. Make a dam around the shaft where it goes into the bearing. The porous bronze bushing will wick the oil in. there maybe a felt washer agents the bearing where it goes into the motor. I would slide it out a little to get more direct access to the bearing.

I am thinking as you said it hadn't ben used much the bearings had dried, or gummed up.

Bill

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Started working on the furnace today. Here are a couple of photos of what I found. Basically, this is what a 43-year-old unused heat exchange unit and burner look like. The heat exchange unit looks brand new. The burner has some surface rust but no corrosion or any problems with the slots. It really looks like the furnace was only used once or twice. The condition of the furnace is why I was willing to attempt the blower motor swap. The motor should be here tomorrow and I expect it to go in easily.

The only thing I have not figured out yet is what to do with the crossover tube that was the subject of the recall years ago. Apparently the rubber tube became dry, developed cracks, and then leaked CO. Mine is still soft and pliable but I really don't want to wait until there's a problem to fix it, especially when I've got it apart right now. The recall fix was to replace the rubber tube with a metal one, but the recall replacement part is apparently NLA. I've got a piece of 3" muffler pipe which I think will work to make a metal replacement for the rubber tube, but I have to figure out how to best gasket it on the ends. The rubber was just press fit onto the flanges at either end. The muffler pipe I have is a very snug fit over the existing rubber tube, so I'm contemplating cutting off about 1/2" wide rings from the rubber tube and using them as gaskets on either end of the metal tube. That combined with some 400-degree RTV silicon for good measure.

Any thoughts or suggestions would be most welcome.tapatalk_1510180556823.thumb.jpeg.82e120e5956170984f8698771cd05e46.jpegtapatalk_1510180561065.thumb.jpeg.c3d6863491ddb7ba170e57df5e484668.jpeg

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Richard, could you get a picture of the crossover pipe and how the ends line up? Never seen one of these setups.

 Trying to get some idea of the peak temperature in the area where the tube is located. 

Think it might be possible to to create  flared ends on the tube and  connect the tube to flared ends at the connection end using  V band clamp the junctions together. The other option might be a stainless steel coupling  to splice the pipe at both ends.

What is the ID and OD measurements of the pipe and the ends you want to couple together ?

Rich.

 

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Here are two photos. One shows the flange on the side of the burner housing. There is a corresponding flange on the blower housing which sits at the other end of of the tube.

The rubber crossover tube is simply a press fit onto these two flanges and is held in place by being sandwiched between them.

The second shows the crossover tube in place. The recall part consisted of replacing the rubber tube with a metal one. I've got a piece of exhaust pipe which is a very snug fit over the existing rubber crossover tube. I'm hoping that I can cut off two rings from the existing tube, each about 1/2" wide, and use them as a gasket between the new metal tube and the flange. That and a bit of high-temp silicon gasket sealant to ensure that there is no movement of the rubber gasket inside the tubes.

20171109_070230.jpg.056f2f7970f7c7dbf6aee70ebac9ad98.jpg20171109_070026.jpg.25559953d80be4f09ea15861e6da8e3d.jpg

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Richard , you might take a look at the sight.

They supply a number of items and something just might work. When doing a job I'm for doing it right or at least give it my best effort.

Thanks for the pictures ! always good to keep the gray mater exercised.

http://www.verociousmotorsports.com/Shop-by-Category/Silicone-Hose-and-Fittings

Rich M.

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Rich - I hadn't thought about just replacing the rubber crossover with something similar but better. I'm guessing that silicone tube like this didn't exist or wasn't widely available in the 70s -80s when the recall was going on.

I found an appropriately-sized high-temp silicone tube on Amazon and it will be here tomorrow. Seems like it will fit, and if so it will greatly simplify putting things back together.

I'm not recommending that anyone else try doing this, but I'll report back to let others know how things work.

I will be coupling the repairs to the furnace with a brand new carbon monoxide monitor. Belt & suspenders.

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Richard, Sounds like a plan ! The way technology changes and the infiltration into everything we buy is mind boggling.

The interdiction of all that technology has resulted in some good items and some that are just impossible to maintain with out the proper test equipment.  $$$$

There was a time when one could set in the engine compartment and eat you lunch, now if you can get you hand or even a finger on something is all but impossible with out removing things.

Good luck !  Rich M. 

New is not always better, but we tend to love bling.     

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Update on this...

Project is now complete other than reinstalling the furnace in the coach. I'll do that as soon as it warms up a bit or gets sunny enough to warm the inside of the coach. Ironic, eh? Fixed the furnace but now it's too cold to work outside.

The motor came in and was an exact fit for the original. The only problem was that the new motor had three mounting tabs spot welded onto the motor case. The original mounted with a wrap-around clamp. A little time with the Dremel took care of that.

The original rubber crossover tube was replaced with a high-temp silicone tube which is sold as an intake tube for guys that hot rod cars. It's four-ply reinforced and was sized nearly exactly to the original. It holds in snugly and I think is going to do the job just fine.

Here are a few photos of the work:

Cutting off the mounting tabs

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Motor back in the original mount

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Motor with blower

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Old (right) and new (left) crossover tube

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Crossover tube in place

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Final followup...

Sun was shining enough today to make it bearable to work outside. I got the furnace back into the coach today. Surprisingly things went pretty well, and other than a bit of frustration trying to get all the ducts and intake/exhaust lined up there were no problems. LP connections did not produce any bubbles on the leak test. The fan kicked on both with 12v and 120v, and it stayed on after the burn until things cooled down. The burner had a nearly pure blue flame, and the pilot looked good. Thermostat seems to do its job. Best part was that the CO monitor read "0" the entire time I was conducting tests. Got the panel in the wardrobe above the furnace put back in, and was even able to staple down a nice piece of carpet to replace the one that was sacrificed in order to get the panel removed.

Best part?? The furnace warms the coach nicely and runs quietly.

Total cost for the repair was $100 for the motor and another $25 for the replacement crossover tube.

Unless I'm missing something, I think that I'll classify this as a successful project.

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