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Furnace Blower Replacement

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The Blower Motor would squeal for about 30 seconds when the furnace started, then about 5 seconds when it shut off. The Motor has oilite bearings, once they are dry,That's it, the only way to do a permanent fix is replace the motor.

I ordered a new motor, and was ready to get to work.

I started this job a few days ago by removing the four screws that hold the furnace in and disconnecting the propane line. The furnace should slide out with some wiggle, but it wouldn't budge. I looked for hidden screws and found none.

I posted questions here and the Yahoo group, Everyone agreed that it should slide out, The one thing I didn't do was remove the exhaust tube, but the furnace should be able to slide out without removing it. (just won't be able to get it back in).

OK, lets remove the exterior tubes and see if there is anything in there that's keeping the furnace from sliding out.

So, I went to the outside and removed the exhaust tube, it slide out easily, However, the intake box wouldn't budge. It was frozen to the furnace. :ranting2:

Since I wasn't going to remove the intake box from the outside, the only option was to leave it attached to the furnace. I used a pair of pliers and carefully bent the four flanges down so I could pull the Intake box through from the inside.

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Back inside, a little wiggle and the Furnace now slid out. I clipped the three wires that went into the furnace and pulled it completely out, intake box and all.

Once the furnace was out, I was able to break the intake box loose from the furnace and then proceed with the motor replacement.

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The flexible tube cover comes off, and the fan shroud comes off to expose the combustion air blower.

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Once that fan is off, remove two screws that hold the motor, the motor and heat blower can be pulled out the other side.

Remove the heat blower from the old motor and put it on the new motor.

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Reinstall the motor into the furnace, install the combustion fan and the shroud. Then hook the blower up to 12 volts to make sure it isn't rubbing against anything.

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Reinstall the furnace back into the coach, hook up the wires, and cycle the furnace to make sure the blower kicks on.

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Hook up the propane, and on the outside, I straighten the flanges on the Intake box, and reinstall it and the exhaust air tube.

That's it, no more squeal.

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Glad to hear that your exhaust pipe would slide off. Mine would not. My last resort was to file off the 2 rivets which held the exhaust pipe to the outside flange. I had to bend the baffle some to do this, and the filing was slow and tedious, but worked. Then I could pull the furnace inside. Upon reinstall I have not figured a way to replace the rivets, but the pipe is solidly corroded together and stays where it should. Motor cost direct from manufacturer was the same as from my local RV dealer--steep. $114

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Here's a closeup of the blower so you can read any numbers off it. Part # 31036 is the blower . Look on E-Bay. do NOT buy a used one, it probably squeals more than the one your replacing :-)

John Mc

88 Dolphin 4 Auto

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Here's a closeup of the blower so you can read any numbers off it. Part # 31036 is the blower . Look on E-Bay. do NOT buy a used one, it probably squeals more than the one your replacing :-)

John Mc

88 Dolphin 4 Auto

If it squeals -take it apart and lube it. Oillite bearings certainly CAN be relubed. You lost me there. I have done many over they years. An oillite bearing is just a bronze or iron bushing that is porous and comes prelubed with 30W oil.

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As for the squealing fan, I've heard people have had good luck reoiling, I've also heard people who oiled, and two weeks later, they are oiling again. $100 is a lot of money to spend for two noisy bearings. If I had time, I might consider installing a sleeve and roller bearing.

Can you reoil them, yes, how long will it last???? unknown. Depends how bad the bearings surface has been sealed over, temperate, etc, etc, etc.

Oillite bearings are not the same as bronze bearings or sleeves. In Oil lite bearings the bearing material is actually a powdery substance thats very porous and I believe they use a Splintering (splattering??) process to make the raw material, very porous) The oil is drawn into the microscopic voids by placing the material in a vacuum chamber and sucking the oil into the tiny voids..

Generally, when the oil is dried up or consumed, there is no more oil to lubricate the bearing. When this happens, the small microscopic pores on the bearing can close up and become sealed, and not allow any more oil to penetrate/flow the bearing to the surface..

Yes, they can be oiled, this is generally temporary in nature and will most likely require constant maintenance as the re-oil will not last as long as the original oilite.

Depending if the bearings are easy to get at and how much they cost, I would attempt to re-oil them. Heat oil in a small can, and drop the bearings in the hot oil and let then sit in there for a few hours. If I had access to a small vacuum chamber, I would place the hot oil in a vacuum chamber and pull a vacuum.

Hey, Like I said, $100 is a lot of money for two lousy bearings, give it a shot, if it doesn't work out, the bright side is, you know how to take everything apart.

JOhn Mc

88 Dolphin 4 Auto

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As for the squealing fan, I've heard people have had good luck reoiling, I've also heard people who oiled, and two weeks later, they are oiling again. $100 is a lot of money to spend for two noisy bearings. If I had time, I might consider installing a sleeve and roller bearing.

Can you reoil them, yes, how long will it last???? unknown. Depends how bad the bearings surface has been sealed over, temperate, etc, etc, etc.

Oillite bearings are not the same as bronze bearings or sleeves. In Oil lite bearings the bearing material is actually a powdery substance thats very porous and I believe they use a Splintering (splattering??) process to make the raw material, very porous) The oil is drawn into the microscopic voids by placing the material in a vacuum chamber and sucking the oil into the tiny voids..

Generally, when the oil is dried up or consumed, there is no more oil to lubricate the bearing. When this happens, the small microscopic pores on the bearing can close up and become sealed, and not allow any more oil to penetrate/flow the bearing to the surface..

Yes, they can be oiled, this is generally temporary in nature and will most likely require constant maintenance as the re-oil will not last as long as the original oilite.

Depending if the bearings are easy to get at and how much they cost, I would attempt to re-oil them. Heat oil in a small can, and drop the bearings in the hot oil and let then sit in there for a few hours. If I had access to a small vacuum chamber, I would place the hot oil in a vacuum chamber and pull a vacuum.

Hey, Like I said, $100 is a lot of money for two lousy bearings, give it a shot, if it doesn't work out, the bright side is, you know how to take everything apart.

JOhn Mc

88 Dolphin 4 Auto

I never said oillite bearing are exactly the same as ALL other bushings. But yes - they are just a bronze or iron bushing that is porous so 30W oil can be somewhat trapped into it. And what comes out can be put back in. They are basically cheap pre-lubed but unsealed bearings.

The oillite lube job from the factory is also temporary - to be technical. Otherwise you wouldn't of had the squealing problem. I've relubed many over the years with very few problems. Actually none that I recall. I had a new Suburban furnace that was never used but squealed after it sat for a very long time and got moisture into it. Thus the lack of sealing. I've relubed electric window motors, RV water pump motors, furnace blower motors, etc. When the bearings are lubed at the factory - they are done the same basic way pressure-treated lumber is treated. The oil is forced in under pressure. Only certain species of wood with open grains will accept pressure treating (e.g. southern yellow pine). With oillite bearings - they are created to per porous to accept lube. It's just a cheat shortcut invented by Chrysler. You can stick a bearing in a small pot of 30W oil and warm it to 200-300 degrees and with the viscosity thinner - the oil soaks in fine. Those little motors come apart pretty easy if you're careful. Usually just a few crimps to undo.

To each his own. No way would I spend over $100 on a motor when it only needed some 30W oil put back into the bearings. I soak them with hot oil and then grease. Standard wheel bearing grease is also just 30W oil that is held in some sort of soap or clay medium so it stays put. If a new motor was updated with maybe sealed ball bearings - I might be more inclined to buy.

If lubing them didn't work - i would of had many failures by now.

Also - generic motors work fine for most I've come across. I got a Suburban NT16 furnace with a missing motor the guy took it apart and ruined it while doing so. I bought a brand new motor for $40. Standard 3" diameter housing and 5/16" shaft sticking out by 1 1/4" with the two-bolt face-mount. They are used in many heating and AC systems in cars, trucks, and farm tractors. They come in single shaft, or shafts at both ends (like my Suburban NT16), and in 1 speed or 3 speed. 3 speed is a nice update if an old furnace was only 1 speed. The place I paid $40 for the new 12 volt motor was just a reseller so he's making money too. With research they can probably be bought direct for $25 somewhere.

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I started this job a few days ago by removing the four screws that hold the furnace in and disconnecting the propane line. The furnace should slide out with some wiggle, but it wouldn't budge. I looked for hidden screws and found none.

I posted questions here and the Yahoo group, Everyone agreed that it should slide out, The one thing I didn't do was remove the exhaust tube, but the furnace should be able to slide out without removing it. (just won't be able to get it back in).

I bought what was supposed to be a unused Suburban NT furnace out of a Sunrader that was sitting in a junkyard. I buy all I can find when cheap and with electronic ignition. The guy told me the owner had just put a new furance in the RV when the 2.4 motor blew to pieces at 60K miles. So it got junked. Been sitting maybe 5 years in NY winters. I wish I'd found it when it was first junked. Looked like it was a nice 18' Sunrader and I would of gladly paid $1000 for it with no engine. Now? Getting pretty bad. Also has the 1 ton full floater in back and matching hubs in front. It must have been updated. Its a 1984 as I recall.

I had a miserable time getting that furnace out. Besides the hornet nest in it, the exhaust pipe on the OD of the fiberglass camper shell was rusted stuck. It is supposed to be a slip-joint - but now it's gotten nature's rust-weld. After getting permission from the junkyard owner, I cut the fiberglass out and removed the furnace the "hard way." Later when in my shop I used a OXY AC torch to heat and get apart with no damage. The blower-motor would barely turn by hand. A problem with time and moisture.

I had one heck of time getting that furnace out and if I didn't have a torch - I'd never have gotten the furnace apart without damage. So I can understand the problems you had with removal.

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I believe they use a Splintering (splattering??) process to make the raw material, ...

Self-lubricating oil impregnated sintered bronze. Oilite, another Chrysler development! :)

http://www.allpar.co...ory/amplex.html

You might find this helpful:

http://www.practicalmachinist.com/vb/general/ot-re-lubricating-oilite-bearing-213850/

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Sintered, or "powered metal" gears are becoming common now in high stress applications. I'm not very trusting of them yet. I just rebuilt a 4L60 GM transmission and the HD upgrade was pinion gears made from powered metal.

Here's a blower and motor from a Suburban NT16.

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100_0815.jpg

And a replacement motors for $30-$45 depending if 1 speed or 3 speed is desired, and/or just a shaft on one end or on both ends.. They turn up for half that price now and then. Standard 5/16" shafts and you cut to the length you need.

3speedtwoshaft.jpg

1shaft3speed12volts.jpg

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Sintered, Thats the word I couldn't think of... (brain damage)

I have a sneaky suspicion that these furnace blowers have a bearing defect. I have never seen so many go bad so fast. This failure is common across all furnaces that use this motor. look at a car heater blower, runs for years and years and nothing like this.

Anyway, try and oil it and see what happens. nothing ventured, nothing gained. :-)

If you try one of those motors that you linked to , let us know if it works out. Could be a less expensive (and better quality) alternative to putting the same problematic motor back in.

If anyone has an old motor, if they could measure the shaft diameter, and also the bolt spacing, this motor that JD found could be a very good replacement.

John Mc

88 Dolphin 4 Auto

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Sintered, Thats the word I couldn't think of... (brain damage)

I have a sneaky suspicion that these furnace blowers have a bearing defect. I have never seen so many go bad so fast. This failure is common across all furnaces that use this motor. look at a car heater blower, runs for years and years and nothing like this.

Anyway, try and oil it and see what happens. nothing ventured, nothing gained. :-)

If you try one of those motors that you linked to , let us know if it works out. Could be a less expensive (and better quality) alternative to putting the same problematic motor back in.

If anyone has an old motor, if they could measure the shaft diameter, and also the bolt spacing, this motor that JD found could be a very good replacement.

John Mc

88 Dolphin 4 Auto

I've had many blowers seize or squeal in car and truck AC and heater blowers. I just had one one apart in my Chevy truck.. The "oil-lite" bearings are a bad choice in my opinion. It is another way of spelling "cheap." They are designed to give lube once a shaft has spun for awhile and created heat to release the trapped lube. OK for a situation where a shaft spends a lot of time turning. Not so good for something that sits for long periods of time and then comes on and off intermittently. Many of them that "squeal" will get quietier if you run them a lot. I also think it was a poor choice by some car companies to use as pilot bushings in manual clutch setups. I've had many of them squeal too - whenever you push the clutch in. A sealed ball bearing - like Toyota uses - won't do that (unless the bearing goes bad).

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If you try one of those motors that you linked to , let us know if it works out. Could be a less expensive (and better quality) alternative to putting the same problematic motor back in.

If anyone has an old motor, if they could measure the shaft diameter, and also the bolt spacing, this motor that JD found could be a very good replacement.

John Mc

88 Dolphin 4 Auto

I've already used the generic 12 volt motors in many things. John Deere tractors, White corn planters, several RV furnaces, my wood furnace at home, etc. I don't use them in cars or truck simply because I can buy new blower motors sold for a particular car or truck new for $15-$20. The RV parts cost $100 because they are not mass used and people buying specialty stuff like for RVs are always getting ripped off. I just bough a new blower motor for my Chevy truck .not long ago. VDO Part # PM102 and cost $15.27 brand new. A brand new blower motor for a Toyota truck is more upscale at $27. VDO Part # PM3715

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I have a sneaky suspicion that these furnace blowers have a bearing defect. I have never seen so many go bad so fast. This failure is common across all furnaces that use this motor. look at a car heater blower, runs for years and years and nothing like this.

I just took a look in my Fasco motor catalog. They are one of the biggest makers of blower motors. The little DC motors with the "oil-lite" sleeve bushings have a service life of 2000 hours or 4000 hours (their are two price grades);

Then the "heavy duty" blower motors have sealed ball bearings and have a service life of 20,000 hours. HUGE difference. I've yet to find a HD blower motor in any RV furnace.

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I seem to recall someone posting that the new replacement heaters were more efficient and make less noise. Has anyone tried one of these, and if so how much difference did it make???

Our blower motor squealed for a while , but doesn't anymore, it is however still quite noisy for sleeping.

vanman

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I looked at Tweetys web site, a new 7900s is about $500 (16k btu). they look the same as the 25 year old one.

I used a WAVE 3 and Mr Buddy last year on my Christmas trip. I'm thinking of just taking the Mr Buddy this year, it puts out 3k or 9k BTU. It kept the inside warm (55deg) when it was 10 deg outside and the wind blowing. Furnace kicked on once or twice during the night. when the Mr Buddy couldn't keep it above 55. These are vent-less heaters so I kept the roof vent open about 1/2 inch.

Heres a link to show how I modified the Mr Buddy so I could plug it into the Toyhouse Propane system. That way don't need to use those 1 lb bottles.

WARNING - DONT DO THIS MOD UNLESS YOUR COMFORTABLE TAKING A PERFECTLY GOOD PIECE OF EQUIPMENT AND TURNING IT INTO A POTENTIAL BOMB.

John Mc

88 Dolphin 4 Auto

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I seem to recall someone posting that the new replacement heaters were more efficient and make less noise. Has anyone tried one of these, and if so how much differemce did it make???

Our blower motor squealed for a while , but doesn't anymore, it is however still quit noisy for sleeping.

vanman

Some new heaters have variable speed fans. That makes them quieter for the times when "full blast" isn't needed.

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I looked at Tweetys web site, a new 7900s is about $500 (16k btu). they look the same as the 25 year old one.

I used a WAVE 3 and Mr Buddy last year on my Christmas trip. I'm thinking of just taking the Mr Buddy this year, it puts out 3k or 9k BTU. It kept the inside warm (55deg) when it was 10 deg outside and the wind blowing. Furnace kicked on once or twice during the night. when the Mr Buddy couldn't keep it above 55. These are vent-less heaters so I kept the roof vent open about 1/2 inch.

Heres a link to show how I modified the Mr Buddy so I could plug it into the Toyhouse Propane system. That way don't need to use those 1 lb bottles.

WARNING - DONT DO THIS MOD UNLESS YOUR COMFORTABLE TAKING A PERFECTLY GOOD PIECE OF EQUIPMENT AND TURNING IT INTO A POTENTIAL BOMB.

John Mc

88 Dolphin 4 Auto

We use the so-called "ventless" heaters in many places. The Mr. Buddy it tiny. We have some as large at 30K BTU output. I would never use one in an RV though when sleeping. At least not when I was sober. They are called "ventless" or "non venting" because they can be used (in many but not all US states) without an actual vent pipe attached. They do require X amount of natural venting (fresh air intrusion). In an RV that would be open vents and windows. It IS nice to have 99% of the propane heating the inside of the camper. The vented RV furnaces use 25%-30% of the propane to heat the great outdoors.

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Correct on ventless. My recommendation to people considering these type heaters, make sure you fully understand the risks, and operation of these units before you make a decision to use them, especially during the night.

Here is a link to a good discussion on the subject.

The Mr Buddy has two settings, 3k and 9k. the 9k did a good job of heating the Toyhouse down to about 10 deg (no wind) I would say the 3k worked ok down to about 35-40 deg. (I like it 70 inside the toyhouse)

At night, I set the furnace at 55 to help the Mr Buddy.

JOhn Mc

88 Dolphin 4 Auto

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JD, probably would not be able to use the variable speed feature for the 7900 furnace, It relies on the blower for combustion air and recirculation air. There is also a sail switch that sense air flow and turns the gas off if it doesn't detect adequate airflow thru the combustion chamber. Probably just tape the MED and LO speed wires up and not use them.

John Mc

88 Dolphin 4 Auto

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We just bought a 1987 Toyota Sea Breeze and took it out to the desert to spend the night. the dealer where we bought it has promised to have the furnace repaired for us tomorrow (1/2) but we couldn't wait so we used our Mr buddy to heat the vehicle last night. It was OK but the little propane tank was used up by 7 AM when we wanted to get up and enjoy the comfort of a heated environment. We left the overhead vent opened about 1/2 inch all night long.

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On the "Re Oiling" Issue. I have had the same common problem of squealing bearings and tried various lubes from graphite to oils. All gave only temporary relief, usually failing as soon as it got cold out. Last spring I tried some Bel-Ray MC-2 O-Ring motorcycle chain lube (with "Moly-Phos") on the squealing exhaust fan in our homes bathroom vent fan and so far the problem has not re occurred. This is an indoor fan in a house with oilite bearings, not the motorhomes heater fan. However we have run that fan every day for an hour or so and have had not one squeak. So today I shot the Sunraders blower fan with chain lube and we shall see how long it lasts.

https://www.rockymountainatvmc.com/p/1935/4287/Bel-Ray-MC-2-Chain-Lube

No longer in stock at the above source, but you may be able to pick some up a local motorcycle dealer, it may be that this is discontinued and you can find it only on retail dealers shelves.

 

 

Bel-Ray MC-2 Chain Lube

belchainlube.jpg

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Ok dolphin lovers, I need some help with my heater. The furnace lights and heats up no problem, but the blower doesn't blow.  After looking at the wire map I exposed the two wires (black and orange) that looked to go to the blower. I touched them to a 12v battery and low and behold the blower started (rather weak), but.... Only for about 20 seconds. The fan then slowed and stopped even while the battery (brand new) was still touching the wires.  All the fuses look good.  I tried to upload some pictures here but for some reason they failed, sorry.  Any ideas. 

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Some thing has been cobbled up on your heater. The fan MUST run to trigger several safety circuits before the fire starts

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