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Old 04-03-2021, 08:29 PM   #1
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Front Duo Therm A/C high speed fan issue?

Hello All, today and for the next 5 days we are in 90+ temps. I ran both front and back AC's with no issue. Actually, we rarely run the units and I have never had an issue in the 7 years we've owned this coach. Today I decided to change the speed on the front unit from low to high. After I changed it, it went to high speed and then a few mins later made a weird noise then eventually made a louder sound and then the unit basically shut down. I pulled the interior vent cover off and could spin the squirrel cage. I ran up on the roof and took the shroud off and didn't see anything abnormal. I checked the breaker in the panel and it was fine. I check the small 5amp? fuse on the circuit board in the front unit and it was good. I was going to check to verify I had 120V to the unit when I couldn't find my small meter. Shoot. I decided to turn on the unit in low speed and the blower came on. I said a few nice words and after a minute or 3, the compressor came on and is now working fine. I'm afraid to go to medium or high speed until after our trip when I get home. When I was on the roof, I studied the motor that runs the squirrel cage and the duct around it seems flimsy and rattles there. I'm wondering if on high speed, the fan gets unbalanced and maybe it moved a tiny bit on the shaft and hit the aluminum casing and caused my problem? I need to recheck the rubber mounts on that motor as it seems as if it can move depending on how fast squirrel cage is spinning. It was too hot up there to do much else for today. Does anyone know if the high speed runs off a different relay, or are all the speeds controlled by the same controller? Anyone replace the rubber motor mounts or take the squirrel cage off for inspection and re-install? I'm sure with more time I can find my problem but being under the gun with 90*+ heat and my family angrily staring at me, it's frustrating. Thanks in advance for any help you can offer.
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Old 04-03-2021, 09:39 PM   #2
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Some have had their fan motor sag do to rubber isolators. Mine seem to flex in the middle the way flat sheet metal gets wobbly or pops One Direction. I used a shim block of green treated wood but I have a fiberglass roof . Yes you're correct each winding will have its own set of contacts . A 3-speed motor has three different windings but I frankly haven't seen just one of one windings going bad but it's possible. It could have tripped resetting thermal overload switch thats inside of motors. I'm not sure it's in your circuit though. A fan is going to vibrate more the faster it goes could be catching a mud dauber nest or there could be one inside of the fan.
I don't think is your issue but...
The fan run capacitor helps to align the amp draw to voltage on sine wave it smooths out a motor a bit , decreases draw and heat.
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Old 04-04-2021, 06:42 AM   #3
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Back ~6 years ago I started to have trouble with my front AC pulling higher amperage and would occasionally kick the breaker. The front AC was louder then the rear also. I went on top, pulled the shroud, and turned the motor by hand, it was almost froze up.

So I found a new motor on line for ~$125.
Pulled the old motor/fan assemble and found that the rubber motor mounts were collapsed, which caused the condenser fan was hitting the sheet metal sometimes. The condenser fan also had a buildup of dirt so while I had it off I cleaned.

I peeled up the sheet metal on the evaporator fan so I could clean both sides. The evaporator fan was pretty clean so just vacuumed if off.

Put everything back together and the AC units runs much quieter, pulls less amps, and cools better.
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Old 04-04-2021, 10:21 AM   #4
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Quote:
Originally Posted by jacwjames View Post
Back ~6 years ago I started to have trouble with my front AC pulling higher amperage and would occasionally kick the breaker. The front AC was louder then the rear also. I went on top, pulled the shroud, and turned the motor by hand, it was almost froze up.

So I found a new motor on line for ~$125.
Pulled the old motor/fan assemble and found that the rubber motor mounts were collapsed, which caused the condenser fan was hitting the sheet metal sometimes. The condenser fan also had a buildup of dirt so while I had it off I cleaned.

I peeled up the sheet metal on the evaporator fan so I could clean both sides. The evaporator fan was pretty clean so just vacuumed if off.

Put everything back together and the AC units runs much quieter, pulls less amps, and cools better.
Thanks. Do you know where you got the rubber mounts or did you just use simple universal ones. I'm sure this is my issue. Just have to wait until our trip is over.
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