Re: stubborn exhaust vent...what if I do this? - Fiberglass RV
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Old 10-06-2020, 09:28 PM   #1
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Name: Bob
Trailer: Bigfoot
British Columbia
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Re: stubborn exhaust vent...what if I do this?

Still trying to remove my Atwood Hydro Flame from my Bigfoot 17DLX, and the exhaust pipe is absolutely frozen (rust or sealant) to the outer vent cap. The end objective is to lube the motor/shaft and try and solve a start-up squeal (maybe a new motor if that is unsuccessful).

What about this....stick my Dremel cut-off wheel directly inside the exhaust tube and cut the darn thing right off. That would free up the furnace box to come out from the inside as well as salvage the two outer vent plates that make up the termination structure. Then, to reinstall, I would sleeve a short 'repair' pipe over the new join, and seal it up with some heat resistant JB Weld epoxy to keep things tight and sealed up to exhaust gas...

thanks for any feedback,
Bob
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Old 10-06-2020, 09:47 PM   #2
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Those furnaces used a sleeve bearing instead of a ball bearing, so my bet is you're going to need the new motor. Normally the exhaust pipe would slide inside the exhaust discharge pipe, so if you can get the outside grill off you'd have a chance at soaking the slip fit with a penetrant like Liquid Wrench. Or, since it's inside a furnace exhaust, you could try heating the inner pipe with a torch to try and expand enough to break loose the rust. I wouldn't trust JB or anything else to not crack with all the road vibration.
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Old 10-06-2020, 11:21 PM   #3
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Thanks! good point about the epoxy. I did a bit more 'research' and it appears something like Permatex Ultra Copper Gasket Maker is a better choice for a high temp seal with added flexibility.
I've already tried the oil penetrant approach, but I'll also try the torch to break the two pipes loose. The outer vent cover won't break free either, but I could gain access to the pipe inside by bending down a stainless 'tang' that sticks up the middle of the opening.

I know the idea of lubing the motor is a bit of long shot, but won't hurt to give it a try. I've read where finding an exact replacement motor is also a long shot. I'm not sure exactly what model furnace I have, as the manual is for 4 different models and I can't yet see any number on it (presumably there will be an identifier that is visible once I pull it out).

Bob

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Originally Posted by tractors1 View Post
Those furnaces used a sleeve bearing instead of a ball bearing, so my bet is you're going to need the new motor. Normally the exhaust pipe would slide inside the exhaust discharge pipe, so if you can get the outside grill off you'd have a chance at soaking the slip fit with a penetrant like Liquid Wrench. Or, since it's inside a furnace exhaust, you could try heating the inner pipe with a torch to try and expand enough to break loose the rust. I wouldn't trust JB or anything else to not crack with all the road vibration.
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Old 10-07-2020, 04:52 PM   #4
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can you access the left side of the heater housing ? I have taken the side cover on the heater housing off, with the fan under the cover; if I push on the shaft of the fan, while it is running the squealing abates. Does the motor and fan turn ? I have had the outer exhaust pipe cover off there was some rust. Can you fit a beehive tool prybar under the outside face of the exhaust. The beehive tool is flat tempered steel, it has a 90 degree bend which is flared out to about 2 inches. it is 3/16 inch thick tapering down to a very thin tip it looks like a putty knife in thickness but it is tempered about a foot long, it can stand a bit of torque. my brother in law and I replaced the Atwood, in his Boler with a new Atwood heater the outlet pipe is not in the same place. we glassed the hole closed, cut a new hole, it is shaped differently. The heater is made in Salt Lake City Utah, USA. can you access the exhaust pipe connection from inside to heat it ? Or hit the outside cover sleeve with a drift from inside ?
Later Kenny
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Old 10-07-2020, 10:41 PM   #5
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Thanks for you experience with this Kenney. I actually had a good day with the furnace today!
Peered into the exhaust pipe again and noticed two rivets that are about an inch inside, to the left and right. I assumed they just locked the two outer vent plates together (the stainless part and the galvanized inner part or spacer). So...rather than cut the pipe in two with my Dremel, I decided to start with those two rivets. Ground them off fairly easily, but still had to use a small pointed drift to drive them out from inside the pipe due to the actual shafts of the rivets still holding on (and I didn't want to make big holes with my cutting wheel). After those were out, lo and behold the furnace was FREE. I didn't have to worry about separating the pipe(s), if indeed there are two pipes fitted end to end - which isn't obvious, at least on the pipe sticking out of the sheet metal housing. In my configuration, which may not be common, the outer stainless cover has two tangs that are bent back inside and riveted to the pipe!! That must be a real joy for RV techs to deal with. When I eventually reassemble, I'll have to use small metal screws to hold the pipe.

After that, I was able to get the motor out, but I haven't had time to get the two fan wheels off. I did however, put my electric drill on the small snub of the shaft on the combustion fan side and I was able to duplicate the squeal for a few moments, so its definitely the motor shaft and not the wheels themselves or them rubbing on something.

As its not a trivial exercise to get to this stage, I think the sensible thing to do now is to replace the motor IF I can find one. I'll have to find a number on it somewhere and start the search...

thanks again,
Bob

Quote:
Originally Posted by Kenny Strong View Post
can you access the left side of the heater housing ? I have taken the side cover on the heater housing off, with the fan under the cover; if I push on the shaft of the fan, while it is running the squealing abates. Does the motor and fan turn ? I have had the outer exhaust pipe cover off there was some rust. Can you fit a beehive tool prybar under the outside face of the exhaust. The beehive tool is flat tempered steel, it has a 90 degree bend which is flared out to about 2 inches. it is 3/16 inch thick tapering down to a very thin tip it looks like a putty knife in thickness but it is tempered about a foot long, it can stand a bit of torque. my brother in law and I replaced the Atwood, in his Boler with a new Atwood heater the outlet pipe is not in the same place. we glassed the hole closed, cut a new hole, it is shaped differently. The heater is made in Salt Lake City Utah, USA. can you access the exhaust pipe connection from inside to heat it ? Or hit the outside cover sleeve with a drift from inside ?
Later Kenny
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Old 10-08-2020, 05:00 AM   #6
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Congratulations on getting it out.
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Old 10-08-2020, 10:10 AM   #7
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If you have access to the bushing to drill a very small hole through it to the shaft you can do that and put a drop of oil there. Better yet if you can take it apart where you can soak the end bells/bearings in hot oil after cleaning them up a little.
Squealing is often from congealed oil and crud tightening up the clearance.
The oil has evaporated and set up.
I had an old 1966 Pontiac Le Mans where the heater motor was squealing like that and instead of replacing I drilled that hole and put a drop on oil on it and ran it another 10 years.
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Old 10-08-2020, 11:18 PM   #8
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Hi,
I will try oiling it, just to see if that changes anything. I"m not sure about drilling a hole, and introducing filings into the 'works'. Taking it apart sounds good, but its always easier than putting it back together
From what I can tell I have and Atwood 7912-1 furnace with a PF 2041Q also called a 31035 blower motor. Of course its one of the most expensive available. I see that MCI makes an offshore replacement motor for under 100, but I think sticking to an Atwood would be preferable? Its around 128. I'm checking/confirming availability, as I only found one site that actually lists it as an 'Atwood' motor.



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Originally Posted by redbarron55 View Post
If you have access to the bushing to drill a very small hole through it to the shaft you can do that and put a drop of oil there. Better yet if you can take it apart where you can soak the end bells/bearings in hot oil after cleaning them up a little.
Squealing is often from congealed oil and crud tightening up the clearance.
The oil has evaporated and set up.
I had an old 1966 Pontiac Le Mans where the heater motor was squealing like that and instead of replacing I drilled that hole and put a drop on oil on it and ran it another 10 years.
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Old 10-08-2020, 11:25 PM   #9
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I'd buy a new motor now while available, and then try fixing the old one. If that runs for 5 years or so, you've already got a replacement!
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Old 10-09-2020, 12:31 PM   #10
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If you can't find the motor at the usual places, try digikey.com. Their user interface is pretty good, at least if you know a bit about the old motor (shaft size, housing size, speed, etc).



Best of luck, and please keep us posted.



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Old 10-09-2020, 01:17 PM   #11
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might try graingers for a motor too.
www.graingers.com
or www.johnstonesupply.com
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Old 10-14-2020, 01:09 PM   #12
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Name: Bruce
Trailer: 1996 Bigfoot B-17-Gaucho
British Columbia
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Furnace motor

Good morning I replaced the motor in my 1996 17 ft Bigfoot, it wasnít easy to find online because of the age . I dealt with this company excellent service. https://www.rvpartsonlinecanada.com/
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Old 10-14-2020, 09:10 PM   #13
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Thumbs up

(update)
I've a learned some things about my furnace in the past few days, and so far, a good outcome...

I've been chasing my tail trying to find a replacement blower motor for a PF2041Q in a '89 17 Bigfoot. Then, I clued into the fact that the present motor I have doesn't appear to be the original, or right motor:/. The only identifier on the furnace, which I didn't take note of at first, is the decal that shows 4 motors, and there is actually a tiny 'tick' beside the one that should be in the furnace. The one that was marked, was the '8012' 1.6 amp motor. What I have, which threw me off track is a 2.8 amp motor (31035 part #) normally found in a 7912-1 furnace - one of the other alternative furnace models.
This isn't a biggie, but the present motor obviously uses significantly more power than the original motor.
Nevertheless, I had completely dismantled things down to the bare motor, so I decided to still trying lubing it as best I could. I 'pooled' a little Turbine oil at the end of the shaft, with the motor 'on end' vertically, and placed a small heat source under the unit to promote a better chance of this penetrating/lube oil seeping in to the bushings. I did this for a day for each side of the motor.
For the last couple days I've tested the furnace and the intolerable squeal has not returned; it belts out a good amount of heat. Yeah!

IF it does return, I've found one supplier that sells an Atwood replacement for my 8012 furnace for only $44. nwrvsupply.com

As an earlier reply suggested, I should order one anyway; my present motor may be on borrowed time.

Thanks to all repliers for your tips in my search!
Bob



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Originally Posted by Bruce in B.C. View Post
Good morning I replaced the motor in my 1996 17 ft Bigfoot, it wasnít easy to find online because of the age . I dealt with this company excellent service. https://www.rvpartsonlinecanada.com/
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Old 10-15-2020, 09:27 AM   #14
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glad your problem is resolved and on an even better path with a lower power consumption to boot.
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