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Author Topic: Problem with roofair  (Read 3155 times)
ArtMaybee
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« on: July 16, 2007, 09:50:41 PM »

Maybe somebody can give me some advice.

I've got an older duotherm roofair. I have no clue what the BTU rating is on it and couldn't find a tag with that listed BTU or a model number.

The squirrel cage fan in it is going out. Is this fan difficult to repair or replace? Can the motor in the fan be rebuilt?
And if replacement is needed, where should I look to find the model number for finding the part.

And lastly, where would the best place to buy the part be?
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TomC
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« Reply #1 on: July 16, 2007, 10:12:44 PM »

Considering you can buy a new one for about $600-how much of your time are you going to spend on this?   Personally, I wouldn't spend the time on an old unit-fix one thing and another goes, etc.  New ones are more powerful, quiet, and reliable.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #2 on: July 17, 2007, 03:26:52 AM »

Hello Art,

The older Duotherm units are no different then the new ones. The blower motors are a doubble shafted and require

removing the evap compartment and the condencer shroud. Please note that the shafts will be Rusty! So removing them

requires hack sawing the shafts and then using a press to remove them from the fan hub. This job is better done on the ground

and not on the roof of your bus!  Just to let you know, Dometic Corp. always sends us a whole new unit if the fan motor goes

bad within the 3 year warranty coverage. Maybe they don't want to pay all the labor expence!

Good Luck
Nick-
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ArtMaybee
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« Reply #3 on: July 17, 2007, 07:59:22 AM »

Thanks for the replies. A replacement unit is probably in order. It's a shame though because the unit works great when the fan turns. Sometimes it just won't spin up. Most times (when it refuses to start), taking off the inside unit, turning the fan by hand, and then putting power back to the unit will allow the a/c to start. Last night it would not start even after turning the fan by hand. It was a bit stiffer than usual.
I'll probably pull the old one apart for the sake of knowledge.

I was told that lubricating the shaft might prolong the unit's life a while longer.
I'm doubtful because the shaft is fairly stiff turning. I'm thinking it's most likely a rusty shaft.
Even so, the only way I could see to do anything about that rust would be to disassemble the entire unit.
Then I have to factor in the fact that I'm NOT knowledgeable (DKS) with these units. I'm guessing there are bearings in the motor which are most likely shot as well.

The only experience I've had with electrical motors were large ones turning pumps in a coin-op car wash.
These were rebuilt repeatedly but were always taken to a professional for the work.

« Last Edit: July 17, 2007, 08:02:49 AM by ArtMaybee » Logged
TomC
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« Reply #4 on: July 17, 2007, 08:02:43 AM »

If you have a rusting problem-like living near the ocean shore, Coleman makes marine roof airs with stainless shafts, etc to with stand the salty environment.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #5 on: July 17, 2007, 08:19:12 AM »

Try squirting some spray lubricant on the shaft where it enters the motor and then get the motor running. If possible squirt some spray lubricant while the motor is running. Enough should get in to lubricate the bushings and/or bearings.
Richard
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« Reply #6 on: July 17, 2007, 08:27:13 AM »

If you try lubricating it use PB Blaster it is the best penetrating oil that I have used.
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ArtMaybee
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« Reply #7 on: July 17, 2007, 08:30:28 AM »

Thanks guys.
I know that a new unit is only around $600-$700 but right this minute the money could be used elsewhere.
If lubricating it would make it last even a couple more months, it would help a lot.

I'd like a bigger unit, possibly even a heat pump. If I have to buy immediately, I'd be stuck going for what I have cash on hand for. I'd rather get what is the proper solution for my setup without regard to price.

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Barn Owl
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« Reply #8 on: July 17, 2007, 09:12:50 AM »

Half of the fun for some of us is getting what we have working again. I have two Durotherms that were manufactured in 1979. When I got my bus I had little hope that they would work, especially after seeing the condenser on one and the wiring in both. All I had to do was charge up one unit (I did it myself and it was on the one with the nice condenser) and make some new filters. On our trip to the beach, we left them on all day and all night, and they worked great. The build plate on mine is located on the top right of the condenser. The more I can do myself (granted much of it is out of necessity and lack of funds) the more my confidence grows. Itís a great feeling. Try the lube, and if that doesnít work, do the motor swap. I like PB blaster also, but my favorite is Marvels Mystery Oil. While in high school I worked in a machine shop that used that stuff for everything. Not only did it do a great job of penetrating (if allowed to sit overnight), it has some very good and lasting lubricating properties. Keep us posted on your progress.
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ArtMaybee
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« Reply #9 on: July 17, 2007, 11:08:32 AM »

Now I just have to figure out what the best way to get in there to lubricate will be.
I'll have to take a closer look at the unit when I get home from work.

Give me some resin, reinforcement, wood, foam, or other assorted things to build a form and I can make pretty nice composite (fiberglass) parts. Stuff like this and I'll have to stumble with it a bit.
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Sam 4106
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« Reply #10 on: July 17, 2007, 02:52:06 PM »

Hi Art,
To access the fan motor on all of the roof airs that I have worked on you need to remove the OUTSIDE cover and the motor is right in the open. I am like Barn Owl, I like to see if I can fix something before throwing money at the problem. Even if lubricating the shaft bearings/bushings doesn't cure the problem a new motor shouldn't cost too much. If you do need a new motor, I would take the motor with fans still attached to an electric motor repair shop and have them test it. It is likely they can provide a replacement motor even if it isn't the same brand. As a last resort you could call Duotherm for a new motor. I have a scaffold that I set up next to the bus and I lay a plank from it to the roof for easy access. Good luck with the project and be careful working on the roof. Sam 4106
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ArtMaybee
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« Reply #11 on: July 18, 2007, 12:29:22 PM »

ok, I got the outside cover off of the roofair. Somebody really messed up the screws holding it on.
I lubricated the shaft on the motor and it it spins nicely now.

I think it's burnt up now though. When you turn the unit on, you can see the shaft try to turn but never starts.

I stopped taking it apart before the motor was completly free from the unit. I wasn't quite sure how to finish taking it out. It looked like I had to remove an allen set screw from a retainer for the squirrel cage fan. This should give access to the screws holding the motor in. I didn't have the correct allen wrench at the time so I called it a night. A new unit is looking better though.
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Len Silva
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« Reply #12 on: July 18, 2007, 01:40:48 PM »

If it turns freely but won't start, it may just need a capacitor.

Len
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« Reply #13 on: July 18, 2007, 03:33:59 PM »

If it turns freely but won't start, it may just need a capacitor.

Len

I remember seeing that Dallas had 1 of those in another post! LOL!
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Dallas
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« Reply #14 on: July 18, 2007, 03:44:58 PM »

If it turns freely but won't start, it may just need a capacitor.

Len

I remember seeing that Dallas had 1 of those in another post! LOL!
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Yup,
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