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Old 03-02-2016, 01:43 PM   #1
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Fixing the Basement Air Rear Duct Work

My experience from 12+ yrs with basement a/c in this coach, is that every few years the cooling just doesn't seem to be keeping up. With the huge heat loss of black roof radius, black upper body paint, and black aluminum window frames conducting heat inside, the a/c has a hard time getting the temp much below 80 deg inside.

So what I've found is the vertical ducting inside the rear cap needs to checked every couple of yrs and you'll find some place leaking. At the bottom, there is a right angle duct that was leaking at the connection to the vertical duct. That was easy to access and fix, and has held up well for many years.

At the top of the vertical duct, where it connects to the "Y", I've found repeated leaks. For yrs I was going in thru a 4" hole in the rear cap by removing the brake light assy. I could get my arm in the hole but only do a marginal repair that way using short pieces of fresh duct tape.

Rather than pull the rear cap, I cut a 14" x 16" hole in back of rear closet to get my upper body access to see and feel the leaks. I used a serrated kitchen knife to cut thru the 1" wall board. Then I was able to re-seal, test, and be assured of no leaks. Afterwards, I put metal tape on the cutout piece, put it in place and from the outside, use a windshield squeegee to get an air tight seal on the outside along with sealing tape on the inside.

I did that job last July in Kentucky when the highs were around 100 deg and the heat index was 118 deg. The a/c began keeping the temps below 80 deg with rig in full sun. Now with 93 deg highs & 60 deg lows in Palm Springs area, the a/c is cycling on/off at 76 deg set. I'm a happy camper!

I believe many folks complaining about poor performing basement a/c units probably have leaks inside the rear cap. If you're measuring about 20 deg drop between the a/c intake vent and the first cold air vents. then the compressors are working up to spec and you're probably just loosing too much volume of cold air with leaks in the rear duct work.

I was hesitant to cut thru the back wall, but when the heat index hit 118, I got motivated and I'm sure glad I did!
Bill & Helen, Last of the Chieftains, 2004 39T, W22, UltraPower, Banks Headers, Koni's, Safe-T-Plus, SMI Stay-n-Play, 2017 Lincoln MKZ Hybrid towed 4-down
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Old 03-02-2016, 02:17 PM   #2
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any pic of where the hole is?
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Old 03-02-2016, 02:46 PM   #3
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Duner, thanks for the update. We must be either fortunate or just not our time for basement air problems, but we have had excellent service and very comfortable temps inside our coach while in Oklahoma and Texas the last 2 summers. I will keep an eye on the duct work in the event we start losing cooling capacity.
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Old 03-02-2016, 05:20 PM   #4
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Thinking outside the box as they used to say. I'll file this on in my memory bank as it is a good idea.
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Old 03-02-2016, 06:54 PM   #5
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Hey Bill,

Hope you and Helen are having a nice time in CA. Man, I was just there and, seems like there is more people now than when I lived there.

Anyway, I don't know if you ever saw my pics of my coach with the tail end off for some body repair but, I thought I'd show them to you to help with your explanation of repairs etc. Removing the entire rear cap would certainly aid in checking out and repairing any of the issues with that ducting but, you could create other problems too.

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Old 03-02-2016, 08:53 PM   #6
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I stuffed my body into that tiny space on my '05 vectra when I saw a frost line on the rear deck. DW handed me tape and cable ties as I put the thing back together. The 40' vectra was never a good place to be in the 118* temps of TX. The basement air couldn't handle it.
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Old 03-02-2016, 09:01 PM   #7
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Hi Scot,
Using your photo, I put a red box approximately where I cut the rectangle. Of course my engine is not back there so there is opportunity to cut the opening a bit lower.

Helen and I are doing well but not my car. Going thru the (skinny) agriculture/produce inspection station on Interstate 8 just west of Yuma, I managed to turn left too soon on the way out and the right side of the car rubbed against the big fat post and did $3600 damage to the car. So we're in Palm Desert for 3 weeks instead of 3 days. Had no idea it even happened til we got here.
Bill & Helen, Last of the Chieftains, 2004 39T, W22, UltraPower, Banks Headers, Koni's, Safe-T-Plus, SMI Stay-n-Play, 2017 Lincoln MKZ Hybrid towed 4-down
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Old 03-03-2016, 10:37 AM   #8
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Another thing to keep in mind if you're having cooling problems is to clean the condenser and evaporator coils on a regular basis. Winnebago recommends cleaning them once or twice a year.

I only mention this because there was a post a few months ago about a basement air system not cooling properly and eventually being destroyed due to "omissions" in the literature supplied by Winnebago.

The poster claimed the unit was destroyed because Winnebago didn't supply information related to cleaning the coils. In reality either the information didn't get passed to the new owner or they never bothered to read it.

As I mentioned earlier the manual supplied to the original owner by Coleman recommends cleaning the condenser coils twice a year. They also recommend inspecting and cleaning the evaporator coil as needed when changing the filter.
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Old 03-03-2016, 08:36 PM   #9
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I had recently fixed a split in the seam next to the radiator. I like the picture as it gives a good idea of the ducting pattern. I used long strips of Gorilla Tape. That should last longer than the duct tape I used last year.
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