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LoggedOff · 10-08-2016, 07:50 AM

I have what I believe is the fan motor starting to go out in my front roof A/C. Yesterday all it did was hum (the compressor I'm assuming). When I pulled off the interior grate and stuck my hand up inside it was pretty hot. After shutting everything down for 15 mins, the unit restarted and is working just fine. But over the past few months I've heard the fan or motor screeching for 15 second periods, then going away for weeks.

I cannot find this fan replacement anywhere. The service manual indicates the Duo-Therm Part # 3109770.002. I cannot find any cross reference. The motor appears to be an AO Smith, which was bought out by Century. Century is saying no replacement exists.

Seems completely asinine to replace the full roof unit (that blows 49 degree air) degree because of a fan motor. Even though I'm sure that's what Dometic wants me to do. Anyone had luck in replacing a fan motor, or guidance?

palehorse89 · 10-08-2016, 08:02 AM

Quote:

Originally Posted by LoggedOff

I have what I believe is the fan motor starting to go out in my front roof A/C. Yesterday all it did was hum (the compressor I'm assuming). When I pulled off the interior grate and stuck my hand up inside it was pretty hot. After shutting everything down for 15 mins, the unit restarted and is working just fine. But over the past few months I've heard the fan or motor screeching for 15 second periods, then going away for weeks.

I cannot find this fan replacement anywhere. The service manual indicates the Duo-Therm Part # 3109770.002. I cannot find any cross reference. The motor appears to be an AO Smith, which was bought out by Century. Century is saying no replacement exists.

Seems completely asinine to replace the full roof unit (that blows 49 degree air) degree because of a fan motor. Even though I'm sure that's what Dometic wants me to do. Anyone had luck in replacing a fan motor, or guidance?

I would take a look at the "Start Capacitors" first, do a search on here, and you find how to test them, or just replace them as they are not that expensive, and see if that fixes your start problem........

ga traveler · 10-08-2016, 08:39 AM

Palhorse 89 is correct. These motors do not go out that often. 90% of the time it is the start capacitor. I would suspect the capacitor way before the motor.

LoggedOff · 10-08-2016, 10:34 AM

Quote:

Originally Posted by palehorse89

I would take a look at the "Start Capacitors" first, do a search on here, and you find how to test them, or just replace them as they are not that expensive, and see if that fixes your start problem........

Yes... I am ordering new Fan Start and Compressor Start capacitors for all 3 units, as well as PTCR's. I've heard they are pretty prone to failing. And, given they are 11 years old and we full-time in this rig...it's only a matter of time. I talked to a tech at Supco and he told me their SPP6 capacitor is a lot stronger and will likely last longer. I'll do anything to avoid full unit replacement, because when these units work...they seriously get the job done well.

Reason I believe it to be a fan motor, is the squealing situation that arises. It's gotten to be more frequent. Did it off and on throughout the day (in 30-60 second episodes) about 2 weeks ago and hasn't since.

One question...am I correct in assuming that the Fan Start capacitor triggers the compressor start capacitor? In other words, it has to release the energy to the compressor? Trying to figure out why things got so hot and what the humming was I heard.

palehorse89 · 10-08-2016, 10:46 AM

Quote:

Originally Posted by LoggedOff

Yes... I am ordering new Fan Start and Compressor Start capacitors for all 3 units, as well as PTCR's. I've heard they are pretty prone to failing. And, given they are 11 years old and we full-time in this rig...it's only a matter of time. I talked to a tech at Supco and he told me their SPP6 capacitor is a lot stronger and will likely last longer. I'll do anything to avoid full unit replacement, because when these units work...they seriously get the job done well.

Reason I believe it to be a fan motor, is the squealing situation that arises. It's gotten to be more frequent. Did it off and on throughout the day (in 30-60 second episodes) about 2 weeks ago and hasn't since.

One question...am I correct in assuming that the Fan Start capacitor triggers the compressor start capacitor? In other words, it has to release the energy to the compressor? Trying to figure out why things got so hot and what the humming was I heard.

The capacitor's store energy for motor starting, cutting back on the amp in rush to the wiring and the breaker's...........if they are failing, wiring and motor's, breakers are maxed out........then something in the system will fail and quit. The electronics's in the system, tell the motor's when to start and shut off..........
http://www.capacitorformotor.com/ac_capacitor.html

sailor_lou · 10-08-2016, 03:11 PM

Definitely replace the caps and PTCR's for the starting issues. Regarding the "screeching" noise, a light oil or spray lubricant on the motor shaft at the bearings ends will work its way in to lubricate the bushings.

LoggedOff · 10-10-2016, 04:23 AM

Thanks... Going to try these things and will update.

LoggedOff · 07-24-2017, 05:39 PM

**Sorry for relighting this thread, but it never got an update, and now the motor has completely froze up.**

Upon digging into this unit, I found the motor to be froze up and no longer spinning. Found a tag on it, motor built by A.O. Smith as part # 48P80A61. It appears that AO Smith sold their electric motor division to Century Electric who still assembles many of the models. Upon reaching out to Century about a cross-reference, they told me it's a Dometic proprietary part that they do build, but I must talk to Dometic about as legally they cannot. Great customer service

. The old Duo-Therm manual lists the part # as 3109770.002. I've searched tons of part sites and it's out of stock every where I go (except for an eBay listing from the Phillipines!)

Has anyone ever had to replace one of these before, and where did you get the part? My past dealings with Dometic always turn into "You Need a new A/C unit". And both times I fixed problems for less than $25. I will rig up a hamster in a wheel before I pay them for a new unit that just needs a fan motor and some fresh capacitors. Looking for some advice...

jacwjames · 07-24-2017, 05:51 PM

I replaced the fan motor on my 2002 Windsor ~3 years ago. The unit started to sporadically kick out and had a noticeable harmonic type sound. I changed the start capacitor but it didn't help.

Bit the bullet and pulled the motor/fan assembly off. The motor was not froze up but very hard to turn. The construction does not allow for bearing replacement.

Here is a site that has info on replacement parts for Dometic products.

https://www.edometic.com/allusr/sp.nsf/spcac?ReadForm

If you have the Model & SN of your unit it may be easier to find a replacement motor.

I got a part number and started doing some searching. I know I found one on Ebay but ended up buying one from Adventure RV. It was an open box sale, I paid ~$110 for the motor.

Replacing wasn't bad. While I had the top apart I peeled back the top sheetmetal so I could clean the unit thoroughly. I used compressed air and blew opposite direction of airflow.

Unit has worked great since replacing the motor, much quieter and pulls less amps.

LoggedOff · 07-25-2017, 06:14 AM

Quote:

Originally Posted by jacwjames

I replaced the fan motor on my 2002 Windsor ~3 years ago. The unit started to sporadically kick out and had a noticeable harmonic type sound. I changed the start capacitor but it didn't help.

Bit the bullet and pulled the motor/fan assembly off. The motor was not froze up but very hard to turn. The construction does not allow for bearing replacement.

You pretty much described this situation to a tee... Exactly how it started and got worse over the past year with the noise and all.