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Old 09-06-2015, 09:06 PM   #1
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Fan making "humming sound", then AC trips circuit breaker

2010 Fleetwood Icon over a 2008 Dodge/Mercedes Sprinter chassis.

AC worked great on shore power & generator during my trip through the southwest this July...

Now when I turn my fan on it makes a humming (straining...?) sound and than when I move my switch to AC (with fan) the AC works for about 30 seconds and than trips the circuit breaker... saw something about a "dirty AC"..?

My fan switch on the thermostat used to have a "high & low" operation, but now only one mode works when fan turned on.

I searched here, but didn't see anything related to my exact problem.

Thanks in advance
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Old 09-06-2015, 09:14 PM   #2
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The blower fan motor on the AC has seized up or ther might be some sort of debris hitting the fan blades. This is causing the blower fan to draw too many amps and when the compressor kicks on the total amp draw trips the breaker.
You can access the blower from the top.
That's my story and I'm sticking to it!
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Old 09-06-2015, 09:54 PM   #3
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Fan making "humming sound", than AC trips circuit breaker

I would have to agree with selah. I think you have a faulty blower motor. When it overheats it is shorting to ground and causing the GFI on your inverter to trip. This could be easy to fix if you don't mind getting up on the roof. The barrings in electric motors stick with age because the factory lubricant dries out from heat and other issues. You will need screwdrivers to take the AC shroud off, lithium grease (ball barring grease) and a precision straight blade screwdriver. If you can get at the fan blade and electric motor, you can spray both barring ends of the motor with white lithium spray. Spray just the barring ends, turn on and run, shut off and spray again, and repeat. I would also check the condition of the ground wire. If it is old and cracked an overheating wire could cause the problem you described. The ground wire is usually fairly easy and inexpensive to replace.


1979 Dodge Tioga Class C 24 foot. 1987 Fleetwood Bounder 34 Foot.
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Old 09-07-2015, 09:30 AM   #4
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Much thanks...

Will remove AC cover and check blower motor resistance (or possible obstruction)

Muchas Gracias...!

I will follow up with a report of the autopsy
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Old 09-07-2015, 09:57 AM   #5
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I am confused with your description of how the AC is working then kicking the breaker.

If the fan will run by itself then it may not be the fan, it could be the capacitor for the compressor or the compressor itself. You can buy a new hard start capacitor for ~$15, which would be the cheapest and easiest problem to fix.

If the fan does kick the breaker it could be an obstruction causing the fan motor to overload. Take the shroud off and see if the fan blade turns freely. If it doesn't turn easy it could be a bearing failure.

I had a similar problem early last year, the front AC unit started to make a loud harmonic type sound and would sometimes the fan would not start on the first try. We normally leave our fans on low all the time so once we got it started it would work. We finished our trip and as soon as we got home I pulled the shroud and tried to turn the blade, it turned "very" hard. I also noticed that the fan blade hit the metal duct work. I pulled the fan & motor assembly, leaving the evaporator fan in the housing. When I got it on my workbench I found that the rubber Isolator mounts had worn out letting the fan sit lower and letting the blade hit the sheet metal duct work. I also found the motor essentially seized. I took everything apart and found the bearings are sealed with no way to easily lubricate. I also found that the construction did not allow for easy replacement without destroying the housing. I ended up buying a new fan motor for ~$100. I took the time to clean the evaporator and condenser coils while I had everything apart. Put everything back together and it works great, pulling a lot less amperage and much quieter.

I have Duotherm AC units, you can look up parts here, but you need your serial number to make sure you get the right parts.
https://edometic.com/allusr/sp.nsf/spc?ReadForm
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Old 09-14-2015, 08:15 AM   #6
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The capacitor is often a leading cause of a malfunctioning AC unit. Well put.


1979 Dodge Tioga Class C 24 foot. 1987 Fleetwood Bounder 34 Foot.
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Old 09-14-2015, 12:03 PM   #7
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Capacitors bad.
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Old 09-16-2015, 09:40 AM   #8
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Quote:
Originally Posted by cimplexsound View Post
The capacitor is often a leading cause of a malfunctioning AC unit. Well put.


1979 Dodge Tioga Class C 24 foot. 1987 Fleetwood Bounder 34 Foot.
Sure is. I helped a couple change theirs a couple of weeks ago in the CG. Took longer to run to town for the capacitor. Any good motor repair shop and some electrical suppliers will have them. $16 and a beer is what it cost them!
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Old 09-16-2015, 09:50 PM   #9
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Capacitor(s) bad

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Originally Posted by milasman View Post
Capacitors bad.
Finally got to checking my fan and it rotates freely and checked the fuse in my wall thermostat... Since I only have one speed now for my fan (no high/low) thought it might be connected

Anyway, there are 3 capacitors on my AC unit
Run capacitor
Hard start capacitor
Fan capacitor

Not expensive : $20 each but wondering if I should replace all three ?

Thanks in advance
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Old 09-21-2015, 04:52 PM   #10
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Replaced all 3 capacitors

Replaced three capacitors and fan works (no high/low)but still has an unusual "humming" sound (but works) then kicks out completely.

Guess I could replace wall thermostat next (probably cost me that much in diagnosis labor?) to see if the "high/low fan" not working is part of the problem.

After that I guess I head for an RV dealer...
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Old 09-22-2015, 09:45 AM   #11
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What Make & Model AC units do you have. Go on the internet and find a trouble shooting guide for your specific unit.

Can you tell what kind of amperage it is pulling with the fan only & then when you put the compressor on???

While you had the top off the AC unit to replace the capacitors did you inspect the blower fan, did you try turning the motor shaft to see if it was free turning??? I had a motor that was going bad, it would start but when the compressor would come on total amperage would kick the breaker. I replaced the motor myself for ~$100.

If the fan is running and then you turn on AC and it kicks it sounds like a compressor issue. If you can't find any other problems a trip to repair facility may be warranted and potential replacement of unit.
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Old 09-23-2015, 10:00 AM   #12
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Fan making humming sound

Quote:
Originally Posted by jacwjames View Post
What Make & Model AC units do you have. Go on the internet and find a trouble shooting guide for your specific unit.

Can you tell what kind of amperage it is pulling with the fan only & then when you put the compressor on???

While you had the top off the AC unit to replace the capacitors did you inspect the blower fan, did you try turning the motor shaft to see if it was free turning??? I had a motor that was going bad, it would start but when the compressor would come on total amperage would kick the breaker. I replaced the motor myself for ~$100.

If the fan is running and then you turn on AC and it kicks it sounds like a compressor issue. If you can't find any other problems a trip to repair facility may be warranted and potential replacement of unit.
Thanks for ur advice it's a Coleman AC unit and will search for trouble shooting guide. Fan turns freely by hand but I'll find out the specs and see if it's drawing too many amps and follow up with a report here
Again, thanks for the thoughtful advice!
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Old 10-01-2015, 09:30 PM   #13
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R/R elec AC fan and it works fine now...
Bit of work to remove condenser fan and barrel fan from old motor assembly due to rust and corrosion
and reinstall on new motor, but it works fine now
Thanks for all the help and advice offered !!!
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Old 10-01-2015, 09:46 PM   #14
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Great job Dave, saved you a few bucks doing it yourself also


Thanks for replying back with your solution
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