Basement air strange behavior

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afchap

afchap

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Joined
Dec 19, 2008
Posts
1,279
Location
...East TX, or on the road...
The past few days, I have thought I hear a fluttering noise in the air flow at the rear or the coach. I could see nothing in the return air area either before or after the filter. Then last night when I went to bed I noticed the output air flow was much less than normal. The AC had been running all day with outside temps in mid 80's. It was doing a good job of cooling. I checked the filter. It wasn't too bad, but I changed it anyway. We set the fan to constant on at night for background noise. Around 2am or so I heard the compressors kick off after one of the dogs woke me. The fan was "on" and running. When I got up this morning I was going to  crawl under the coach and check the output duct to see if it had come apart behind the rear cap, but the output air flow volume is back to normal!

Can the coils on these things freeze and restrict air flow?  We had #1 compressor replaced a year ago and the unit has not been up to previous performance since in terms of cooling. The tech swears he got it fully charged, but if he did not, could the coils ice up and restrict air flow? Is there any insulation/etc inside the rear duct that could come loose and plug the air flow?

We'll be in the Wichita area over the weekend and I'm thinking I may call the guys at Flint Hills RV in Andover that did an excellent job on fixing it several years ago.
 
I was having similar problems, and I replaced the air filter. Mine in on the bottom of the night stand in the bedroom. you can get a replacement at Wald mart, Loews, or Home Depot

Try that first.
 
Paul - if it is undercharged, it won't freeze much less get very cold.  There have been cases of the molded "Y" in the rear cap where the duct is split into two runs splitting and dumping air.  Feel along the inside of the aft hanging locker for unusual cold and also on the outside of the rear cap.  What is the temperature of the air coming out of the rear most ceiling outlet?
 
That's very interesting.  I have no formal education in HVAC but quite a bit of hand's on experience.  I can say that I have never experienced a freeze with a low Freon situation.  Maybe there are certain parameters that make this an unusual occurrence...
 
I had read that freeze-up due to low freon is possible. I talked to a tech today in Andover KS who said that is indeed possible, and for to cause reduced air flow, in the right temp and humidity conditions. Unfortunately they are booked for all next week and we can't wait around. I'll check again for duct leaks when not parked on mud, and hope for the best. We are headed for Montana for an Alaska caravan so likely won't need super cold ac much this summer...
 
This may sound weird, but I had the same issue, hearing a fluttering sound.  What it turned out to be was my drain hose duck bill stuck and water moisture that collected in the unit didn't drain.  The fluttering sound was the blower turning and spraying water all around the inside.

I never would have found this because I still saw water dripping out when the unit was running.  A small amount of water was leaking out of the seams of the unit housing.

I found it when the water level rose so high that it shorted out the blower start capacitor.  Upon opening up the side of the unit, that is when I discovered the full extent of the problem. There was 2-3 inches of water in my unit.

I installed a new capacitor, stuck a screw driver in the drain hose to open it and after a day of letting the unit dry out with the panel off, I put everything back together and it ran fine, with no more fluttering sound.

I now periodically check the hose duckbill to make sure it is open. 

Best Regards!
 
One further note, here is a post about what I'm talking about from my blog, with pictures:

http://rsanityrvtravels.blogspot.com/2012/09/how-it-all-ended.html

Best Regards!
 
I am a HVAC tech by trade. An evaporator will indeed freeze up when low on Freon. R22 systems are designed to run a 40 degree coil, with 75 degree air moving across the coil will leave a discharge air temp of 55 degrees. If you have a low air flow problem and high humidity, the coil can start building frost. Once that starts it can freeze solid. When a system is short on gas the evaporator will run at a lower temperature, and start building ice on a portion of the coil that has liquid refrigerant present. When that happens, airflow is reduced, thus building more ice. Once a system is low enough on refrigerant, no liquid will be present in the evaporator, thus no cooling what so ever. If you suspect a low refrigerant condition, you need to get service right a way, as the cool returning gas is what cools the compressor. 
 
One thing to check is the duct that runs from the ac unit behind the back cap and supplies air to the duct system inside the coach.  With a flashlite look up along side the plenum  for loose tape at the joint along the side. Mine had come loose for about 2 ft. I was lucky the loose tape was on the inside and I could access it from the engine compartment.
 
With both compressors running, my indoor coil has frozen from day one (2006).  Living in dry climates and high altitude is one of the reasons..  The other reason is low air flow across the coil period.  ::)
 
Why would being in a dry climate cause the AC to freeze up? Low humidity should mean less dehumidification.
 
mrschwarz said:
Why would being in a dry climate cause the AC to freeze up? Low humidity should mean less dehumidification.
Click to expand...

Not sure why this happens...it just does, and always has done this.  We are going to Texas soon, and I'll get the constant drip, and the coils wont freeze.
 
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