Basement A/C Argh...

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JLModer2

JLModer2

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Joined
Mar 20, 2009
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Fulltimer, Currently in Dallas, TX
I am having some issues with my A/C.  2001 UA 40J. 

It has been a hot summer, and now that it has cooled off some, we have been having lots of rain and lots of humidity, and it seems to be be freezing up.  I am pretty certain of this since it will blow cold, then gradually the airflow decreases to almost nothing.  IF I reverse it and run it in heat mode for a bit you can hear the ice dropping off the condenser, then it works fine for a while (lately seems like once a day I have to defrost.)  I don't recall everr having this problem before....

My filters are changed regularly, and still does this with a new filter.

It helps to have the blower always on, as when it cycles it obviously thaws out some.  When the compressor kicks out you can immediately tell because of the moist air it is pumping inside.

I do need to check the wiring this weekend, but I have never really been able to tell much difference between Low and High on the blower setting.  It seems to push about the same amount fo air.  I can hear a faint click when I switch it, and maybe a reduction, but nothing I could quantify by any means.  It is blowing cold, so I don't think it  is a freon issuse.

Could it be just the high humidity?  Or do I have to figure out how to drop this thing?

John

 
I've heard lots of interesting issues with these units, but I have never heard of the basement air unit freezing up. It sound to me like something isn't working right. I wonder if the return air flow to the unit has been compromised so it is sucking humid air rather than air from inside the coach? ...bad seal between return duct and unit maybe, or outside air mixing with inside air in the unit somehow???  With lots of humidity, it should be putting lots of water out the drain on the bottom of the unit. I would check that, and if it isn't, begin to look further. I would likely contact either WInnebago OR at email [email protected] or telephone (800) 537-1885 or RVP at e-Mail Address [email protected] or telephone (316) 832-4357.

You are right there there is very little difference between the low and high fan speeds, and when the unit is on heat there is only one speed period regardless of where you set the switch.
 
John

I asked on the Winnebago owner's forum on Yahoo if anyone had heard of this happening ... here is the answer I got...

"Yes, if the thermistor goes bad.  It helps sense near-freezing conditions and allows it to thaw out.  Unfortunately, you have to pull the A/C unit to replace this $10 part."
 
There are plenty of us that have the same problem.......this is not uncommon with these basement units.  ;)

John, you have a thermistor problem....this device will be inserted in the inside coil, and is designed to cut off the compressors when your coil freezes.  ALWAYS...and I mean that...ALWAYS leave your indoor fan set to "on" and "high", as high air flow across this coil is very important. As stated above, call RVP, and have them send you another thermistor, and make sure you insert it on the INSIDE of the coil fins about 4" from the top and about 2" from the side.  Make sure you have a clean filter, and nothing is in front of your air intake also.

I also agree that there is not much difference in the low and high settings of the air flow.  I forgot what the difference in the air flow CF was between the two, but it is not much.
 
Alight, Thanks guys.

I think AF might be right, I might be sucking in outside air too.  I really need to pull the unit and check it over and clean it up.  I jsut hope mine is installed like "dunners" and it is easy to get down.

John

 
Ok, I didn some maintenance on it today...

I checked all the electrical, and both blowers are coming on high and low, both compressors are also working correctly, and everyhting is drawing about what it should for power.

I vacuumed the coil and straightened all the fins.  I don't see any gaps around the rear (intake), but I did see where on the outtake the screws were loose so I tightened them.  I also checked it over as far as pulling the tunit and now think I can manage it, as Duner's instructions were pretty close to what I have even with the diesel.  It does look like the lower frame will need to "Tilt" down to allow the front top out of the 'Cage', but there appears to be long enough bolts that loosening them will allow that.  The side outtake looks easy enough to take off, and seems to have adequate wiring I wouldn't have to disconnect it.

I do think there might be a thermistor problem.  Right now I am torn on what I should do, as I did find a new unit for sale for $850 plus freight.  My thinking is if I did pull it, I am going to want to go through it, and I might be better off just replacing the entire unit since it is 8 years old.  Either way I will have to nurse it along a while till we don't need it daily at least...


Thanks for your suggestions!

John
 
I would have RVP send you a new thermistor....it would save you $850....just a thought.  Pull out your air filter, lean down and look at the internal coil....you should see the thermistor sticking in the fins.....I could replace it without removing the unit..... ;)

You should clean the internal coil also......
 
I keep going back and forth...

Mine is in such a way I can't really reach or see down into the unit from inside.  I do not have a bedroom slide, and my bed is north/south.  The cold air return is on the side of the bed, and under the bed there is just enough room to slip the filter in lengthwise, and even if I took out the grill grate, I don't think there is enough space for me to get my arm down there....

I Know after 8 years those bushings on the fans must be shot...  I probally should just order the new parts and pull it and clean it out really good.  We will see.

Thanks for your input.

John
 
might wanna make sure that the condensate drain hose is open and not plugged, especially in high humidity areas.  You should see water dripping out of this hose when the a/c is running.
 
My basement air was not working properly when the unit was new. After checking many things I found a split in the duct board plenum about two or three feet above the a/c.  I was able to replace the foil tape by removing a part of the shroud above the radiator on the passenger side. I donot know if this would cause freeze up but it sure did improve the volume of air into the coach.

dfdret
 
I wanted to report back, a friend (BucknJeff) suggested that I try only running one compressor when the temps are not so far apart and the humidity is high, and that seems to be the answer!  It has not froze up since.  It does take a bit of monitoring to keep the coach cooled off, but it keeps the air flowing, which makes a big difference!

Some of the fix may have been the outtake plenum also, It very well could have been sucking humid air in and causing the problem.

Either way, thanks for all your suggestions.


John
 
I am a HVAC technician, and if your freezing up it usually indicates a LOW freon charge, if you see frost on return line to compressor ot top of compressor is frosted it is a indicator of low freon. The thermistor is a safety device not a system control device.
 
If your inside coil is freezing and the thermistor is not cutting off the compressors, you have a thermistor problem...either in installation or electrically.

Our inside coil freezes up occasionally (in Denver sometimes) and the thermistor will cut it off....and we aren't low on freon.

Also, running one compressor will really show you that.....um....one compressor works, and won't have the ability to freeze up your coil....but closing the breaker and running TWO compressors will freeze up your coil...
 
It is very common for these Winnebago units to have a leak/disconnection in the duct going out of the unit ... most common locations are at the "L" where the duct turns upward just after it leaves the unit, or about half way up the inside of the rear cap. The result is that on a hot day a good bit of the cooled air never makes it into the coach and the unit has to work much harded trying to keep the rig cool. One way to tell if you might have a leak is to check the air temp at a vent when the unit has been running for awhile. When running well, my infrared thermometer will show the air flowing from the ceiling ducts to be in the 40's or colder.
 
I've got a brand new unit and had the duct repaired and there is noway I get 40's or below in the summer. I will check now/fall but I dont think I will get 40's or below. Heck I've read where some folks get 9-10 mpg while I get 6-7. My mh is always below avg. :(
 
winnie35 said:
I've got a brand new unit and had the duct repaired and there is noway I get 40's or below in the summer. I will check now/fall but I dont think I will get 40's or below.
Click to expand...

Are you talking about the temps at the outlet ducts?  As I recall, in the summer I'm running in the 40s or low 50s as measured by a non-contact temp gun.  Our interior might be in the high 70s or low 80s, but the air coming out the ducts is plenty cool.
 
Seems to me that the only way to get to 40? out the ducts is when the indoor temp is about 60? (Differential 20)

With 90? inside, the max you will get at that time is about 70?.  RV's have a closed system. The outside temperature only affects the ambient inside temperature due to poor insulation, general heating of the entire bus. Leave a window open and you will have problems.

  The air is recirculated and drops 20? from the indoor temperature only.

I guess what I am trying to say is that the A/C does not produce 40? but rather decreases in temp when the inside temp decreases, in 20 ? increments.

I hope I made sense..

carson


 
the A/C does not produce 40? but rather decreases in temp when the inside temp decreases, in 20 ? increments.
Click to expand...
I have read that statement many times before but have found it to be untrue for my unit. Like John reports, my system consistently provides output in the 40's when inside temp is in the 80's.  I just checked again with an infrared thermometer and the output today at the ceiling vents is 30-35 degrees colder than room temp.
 
carson said:
I guess what I am trying to say is that the A/C does not produce 40? but rather decreases in temp when the inside temp decreases, in 20 ? increments.
Click to expand...

Interesting point. In Texas, I measured about 59? at the outlet with 84? at the return, which I though was pretty good. For those of you who have measured the duct temp in the 40s, what was your return air temp?
 
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