Furnace Fan Motor Failed, Lessons Learned

[D2Reid]

It's Monday, still no fan motor from Suburban. 15f last night, didn't freeze pipes. Extra heater from wallyworld is helping. I think we are being saved from freezing solid by our skirt, so glad I got it.

[Jims94vmx]

That sucks waiting so long!!! Hope you are not paying for electric......

[D2Reid]

That sucks waiting so long!!! Hope you are not paying for electric......

Good news bad news.

Bad news. We leave here in 8 days. Will the fan motor come and get installed before we have to go, or will it be a further major headache. Staying is not an option.

Good news, we changed over to daily rate on the first, no longer paying for electric.

Bad news, daily is way more expensive than prorated monthly, even with paying for the extra electric.

Good News, we have had a couple of chilly mornings but overall have been pretty comfortable.

Bad news, temperature is forecast to drop and stay there for several days.

Good news, we take it all in stride. I could order a motor overnighted, couple hundred bucks and end these shenanigans, or I can wait it and see if Suburban ponies up and pays the whole bill. There are not right answers, only decisions that we make that take us down a different road.

[D2Reid]

Tech was here a week ago yesterday, still not fan motor.

[orbiker]

Dallas
The part number you supplied is available on Amazon.
You could next day one from Amazon and install it. When the Suburban fan shows up, process the paperwork for the job. The Suburban fan could then be your spare.
KEN

[D2Reid]

Dallas
The part number you supplied is available on Amazon.
You could next day one from Amazon and install it. When the Suburban fan shows up, process the paperwork for the job. The Suburban fan could then be your spare.
KEN

Temps are supposed to dip in the next few days. So I had made up my mind to do just that, but before I got to the computer to order my tech texted me that the motor has come in and he will be here today around noon to install it.

Next hurdle is to see if Suburban will pay the tech appropriately. If they don't I will, he has been great in dealing with Suburban, most won't.

[Jims94vmx]

get the install done?

[D2Reid]

Hurray we have heat. While you can remove the fan motor assembly and control board on an SF-35Q it's probably wiser to remove the whole heating unit to do the replacements. So here's the rest of the story.

Suburban agreed to pay all of the mobile techs fee's, Suburban sent a new motor without charge. Old motor was definitely toasted. I tried upgrading the control board to a new us made Dinosaur board, tech thought is was the correct board and would work with the SF-35Q, it didn't. Once it was installed the fan motor came on and would not shut off. Lesson learned, if you are going to replace the control board with an after market make sure it is compatible. No harm done, put the OEM board back in.

Getting the fan wheels off of the old motor shaft was tough. Galvanic action had set in and they were nearly welded on. And yes, the set screws had been removed. Had we known it was going to be such and issue we could have put a couple of drops of penetrating oil on them ahead of time.

Pull the fuse. There are a lot of places the power can touch grounded stuff and short. We went through 4 15 amp fuses.

The ground wire for the motor is behind the last shield. I would have been much better to have cut that wire and splice the new ground wire in rather than pulling that last shield out. The new motor assembly slipped while we were messing with the last shield and busted the squirrel cage, cheap plastic. Oh crap, another weeks delay, not. Of course none of the local shops carry parts for the SF-35Q, gotta order them. Found an outfit that would overnight us the squirrel cage, $20 for the part, $55 for overnight. The tech cannibalized an older furnace he had at the shop and brought a similar sized squirrel cage, the only noticeable difference if the replacement was metal not plastic. This is both good and bad. Good he got a replacement within hours not days, bad that it is metal, good that it is metal; let me explain. The metal cage weighs more than the plastic one, like double. It takes more energy and resistance to get the heavier cage moving. This wears the motor out faster. Plus the weight on the shaft bearings is greater, additional wear. Essentially this should reduce the life expectancy of the motor. On the flip side the metal cage is more robust and less likely to have a catastrophic failure due to fatigue. It will last longer. Once the cage comes up to speed there is little difference. I cannot prove it, but I think the heavy metal cage pushes the air more efficiently than the lighter plastic cage. The heavier metal cage is less susceptible to imbalances due to debris build up. The biggest advantage to the heavy metal cage was it is free and there, no more delays. So I went with it.

The tech said Suburban was paying the whole bill and I owed him nothing. I am a little shocked. I didn't expect that to work. I always have to pay something, it's weird, but in a good way.

Here's an odd observation. When the fuse was blown for the furnace the thermostat controlling the furnace and A/C unit lost power and was blank. So if you blow the furnace fuse in the panel you cannot turn the A/C on. Tech explained that the power from the furnace fuse goes to the control board in the A/C unit, no power, no power to A/C control board, no power to the thermostat. I think that is horrible, but it is what it is and now I know that if my thermostat quits working to check the furnace fuse first, then check the fuse on the back of the thermostat. It was very odd. It will take further research and experimentation.

Bottom line: we have heat tonight, thank goodness the temps are supposed to go into single digits this next week. We got real lucky with warm temps.

[Cate&Rob]

Hurray we have heat.

Hi Dallas,

Good to learn that you have heat! You have had quite a journey. Thanks for the detailed explanations of each step . . . this will help others. I did know that the thermostat talks to the AC and the AC talks to the furnace . . . odd as this may seem.

I still think that for those who live in their RVs in sub-freezing temps, the furnace is a critical component. I would be finding space to carry a complete spare . . . its not that big. We can live without AC or hot water . . . without heat can be life threatening.

Rob

[orbiker]

The tech said Suburban was paying the whole bill and I owed him nothing. I am a little shocked. I didn't expect that to work. I always have to pay something, it's weird, but in a good way.

Nothing is good.

Is it possible to change the control board with the furnace still in the RV?

How do you know if you have the correct dinosaur board?
Thanks, KEN