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Author Topic: DuoTherm AC Works Only When Fan is Spun by Hand  (Read 381 times)

kjjones

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DuoTherm AC Works Only When Fan is Spun by Hand
« on: July 13, 2020, 08:17:04 PM »
I'm having an issue with my DuoTherm AC. It has been working great , every day for a month until it shut off today. When I tried to kick it on, the fan would not turn. When I spun the fan by hand, it took off and ran fine. I did not feel any resistance in the fan at all, it spun freely.

The next time I turned it off then back on I had to spin the fan again to get it to start.

At this point I'm not sure if I am having a capicitor issue or am in need of a new motor. This is my first RV AC and I'm not really sure where to begin. Any help is greatly appreciated!

Update: I looked up the inside and it looks pretty frozen in there. Would these issues be related? Or does it sounds like I have multiple issues at hand?
« Last Edit: July 14, 2020, 05:39:39 AM by kjjones »

Arch Hoagland

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #1 on: July 13, 2020, 08:34:41 PM »
The impeller had loosened up on mine and moved a bit on the shaft so it was rubbing and wouldn't start all the time.

Or it could be your start capacitor is causing the problem.

I don't think I'd replace the motor until I ruled out the starting capacitor.
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 90,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

darsben

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #2 on: July 14, 2020, 08:16:55 AM »
If the compressor comes on without the fan rotating then it is NOT the start capacitor. You should be able to hear the compressor when your thermostat calls for cool.
1990 Fleetwood Southwind on P30 chassis located in
Central NY in summer and beautiful Casa Grande AZ in winter

Lou Schneider

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #3 on: July 14, 2020, 10:18:35 AM »
The fan motor has it's own run capacitor.  Classic symptom of failure when the fan picks up and runs after given a spin.

kjjones

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #4 on: July 14, 2020, 10:45:11 AM »
The fan motor has it's own run capacitor.  Classic symptom of failure when the fan picks up and runs after given a spin.

So is the run capacitor replaceable by itself, or is it time for a new motor?

Lou Schneider

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #5 on: July 14, 2020, 11:00:43 AM »
It's replaceable.  It's on the roof side and shouldn't be hard to find.  You may have a combined capacitor (compressor and fan connect to separate terminals in a single can) or a separate two terminal capacitor.

Be careful - the purpose of a capacitor is to store voltage.  Make sure the incoming power is off (unplug the trailer or turn off the circuit breaker) and short the capacitor terminals to discharge any voltage before you work on it.

« Last Edit: July 14, 2020, 11:15:08 AM by Lou Schneider »

John From Detroit

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #6 on: July 14, 2020, 05:28:18 PM »
If the compressor comes on without the fan rotating then it is NOT the start capacitor. You should be able to hear the compressor when your thermostat calls for cool.
Z

NOT nevcessarly true. both motors may have START caps or the start cap can be a dual 1 side for the compressor one for the blower.. Mine are like that.

So it could be the start cap
It could also be the start winding
And the start switch. (That's internal to  the motor if it exists)
Nothing adds excitement like something that is none of your business
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FullM3talJack

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #7 on: July 22, 2020, 12:03:29 PM »
Same issue I had on my Duotherm unit last year. Hopped on the google machine and found the exact specs of the run capacitor, then ran down to my local Grainger and grabbed one for 16$. I was taking a mildly educated guess at what was at the root of the problem, based on my electronics experience in the Navy, and figured that, at best, if it worked, I look like a genius to my wife and only spent 16$ to fix the AC in mid July. At worst, I look like an idiot to my wife because I guessed wrong (normal day in my life), but I'm only out 16$ and still have a new capacitor in the unit when it does get fixed. It turned out for the best, and is still running like a champ a year later.

Best suggestion I could offer if you're going to try and change the capacitor is to watch a few youtube videos on the topic, as applies to your model of AC. If you change a capacitor that isn't bad and is still holding a charge, and you touch the wrong thing, the capacitor will let you know quickly. It hurts.

Arch Hoagland

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #8 on: July 22, 2020, 02:11:06 PM »
FullM3talJack said:  ", based on my electronics experience in the Navy,"

Were you an ET?
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 90,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

FullM3talJack

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #9 on: July 22, 2020, 03:37:04 PM »
Almost, but not quite. I started my career in the Navy as an AT, finished it as an MA after 9/11.

TheBar

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Re: DuoTherm AC Works Only When Fan is Spun by Hand
« Reply #10 on: July 22, 2020, 09:06:56 PM »
You said it looks frozen in there. My guess is ice is stopping the blower. You may be low on refrigerant or you may be in really high humidity. Try turning  the thermostat up a few degrees to see if that helps.
Retired computer automation programmer
1997 30' Class C plus 2008 popup
DW loves camping more than I do!