AC air flow problem SOLVED

We have an early 06 3400rl. The ac put out some really cold air, but the ducts and ceiling venting air flow seemed a little lame. The one thing I did notice is the silly bathroom vent worked better than any. Scott has mentioned that its because its closest to the ac. And that makes sense. Another thing I noticed is that with the grill open for quick cool, the vents blew about the same as when it was closed.

Here is what I did to get it going.

The first thing I did was pull off a couple of the grills and take a mirror to make sure the vents were not smashed and the end caps were intact. That all seemed fine.

Next I cleaned up the flow of air, in and out of ceiling. Just under the ac. Cut away roofing material that blocked air flow. And smoothed up the edges and sharp corners where air flows with some foil duct tape. Cost about 7 bucks. What I was trying to do was remove anything that would slow down the air flow or create back pressure. That helped some but it still wasnt great. The bedroom was still lacking flow.

If you look up under the ac in the ceiling, there is a small area where the cold air comes down. It is just then expected to turn a sharp corner and get into the ducts. Well I guess my air didnt understand what it was supposed to do.

So what really solved the problem for me was a little 3"x5" piece of aluminum bent into a curve to catch about half of the air flow and smoothly force it into the off door side ducts. Worked so well it blew all sorts of junk out of the vents and onto the floor. You can now lay in bed and actually feel air.

It was just about 100 here the other day, it took about an hour and a half to get the rig comfortable. Inside temp was about 95 when I started.

TimK

Tim,

Great fix! My rig seems okay but on the hottest camping day last year, it was hard to cool down.

I'll be taking off my chill grate tomorrow to wash the filter and I'll check out my edges and such. Still got plenty of that foil vent tape and I need to make a run to Ace Hardware anyway - may as well try your smooth radius diverter fix.

Post a couple of pics if you can.

Jim

ao air flow

how about a picture ?

Kerry

Take the pictures and send them to the factory! Our 3055 is suppose to be built in the next few weeks. Would be nice if the air worked right from the factory.

Details/Dimensions of Dometic 15M BTU AC with Heat Pump

Looking forward to seeing Tim's diverter modification.

Until then, I took the entire plastic cover off the inside of my AC and took some pictures.

For those contemplating a mod to theirs or just curious, here's what I found:

Removing Cover:
- Remove air filter
- Remove 4 screws behind air filter
- Pry out plastic plugs and remove 2 more screws (see image 1)

Orientation:
There are two distinct sections inside my AC. The section towards the front of the trailer is the air intake section
The section towards the rear of the trailer is the air output section

The output section has an access hole that is 9-3/4" x 3-3/4" In the top center of the output section is a 4" x 4" hole with a squirrel cage type fan in it. Output air blows down out of this 4" x 4" opening and into the output section (plenum area?).

On either side (Left/Right or Door Side and Off Door Side) of the output section is a rectangular hole that leads into the ducts that run down each side of the trailer within the roof trusses. I measures this duct opening at about 1-3/4" tall x 7" wide. As you can see from 2 of the images, the ducts have the foil tape at the seams where it joins the plenum. After taking the photos, using my hand, I pressed on the folil around the perimeter of the duct to smooth it out.

The vertical dimension from the bottom of the 4" x 4" output opening to the 9-3/4" x 3-3/4" opening is 5".

Thanks to timk, I am thinking hard about making some sort of radiused diverter out of sheet metal (galv. steel, aluminum etc.). I was thinking of making a dual sided diverter that looks like a step mountain peak.

Thinking.....

Jim

Jim,
I did take some pictures. But yours put mine to shame. Will try to get some better shots.
TimK

Hope the picture upload thing works. It was unable to get a good picture to really show what I did, so I made a cross section drawing of the the area below the ac. Another thing that I did this morning was to tape off the area beyond the last duct opening. Don't think it did much, but it gave me something to do.

You might notice that a good part of the area where the quick cool grill air exits is covered. I did that this morning as well. Originally I only did the diverter to the off door side, thats what made the biggest difference for my rig. After doing the door side diverter the quick cool grill does not work as well, but leaving it open it is a lot quieter, and works about like the other vents. So in my mind the positive effects of the door side are still questionable.

No I am not an air conditioning engineer, but I did park in front of a Holiday Inn last night.

TimK

Way to go Tim maybe Heartland can pick up a few tips from this and finally get this AC issue sorted out.

Trap

Tim,
I want to thank you very much for your photos and especially the drawing of how you solved your a/c distribution problems. When we get our 3055 back out of storage I am sure that I will do the same thing that you have done, since or a/c seemed very weak on our first time out also. Again,thank you and also Jim Beletti for the photos and help!

Mountain good idea

Jim,
I think you have a great idea there about making the mountain to divert the air both ways. Perhaps even attach the mountain to the plasitc cover (the one with the 6 screws)that you show in you photos. That way any adjustments could be easily made and wouldn't be as permenantly attached to the rest of the inards. Thinking also.............

Tom,
Its mostly foil duct tape and light aluminum. It would be very ez to get out if you needed to. I would think it might be hard to get a good fit by attaching to the white plastic cover, but yours might be different.
good luck,
TimK

Hope you A/C engineers don't void your warranty!

Thanks for the info, we just spent our second weekend in our camper, the AC is terrible. One AC cant keep up, it ran from 10 am till 7 pm and it didnt get below 80+ in the den. No air flow.

ChopperBill said:

Hope you A/C engineers don't void your warranty!

Click to expand...

Hah... we got duct tape, dont need no stinking warranty.

Additional Vents added

We after the Rally seminar by Dometic , where the AC was discussed at length, I thought i would need additional vents anyway. I needed to take the BH to the dealer any way for the toilet bowl seal So I made a seat of the pants decesion to add 3 AC vents .. The Off door side duct got 2,,One went in the Bedroom and another in the livingroom and the doorside duct got one, that went in the livingroom..Air flow has been increased and you can now feel air while sitting in LR or BR..This weekend was very hot 95 and humid. RV took about half the time to cool as is usual, meaning now it's about 4 hours undisturbed. But we had guests in for dinner and many dog walkings required the door to be open a lot .All in all , I feel a well spent 160 bucks..The tent in the vent mod will be next. I also have been in side the airbox plenum and sealed all cracks and airleaks with foil tape..

Great decision Frank and thanks for sharing the results. I too and pondering having 4 more vents put in at the end of this season when I go in for some service work.

Just this afternoon, I picked up a 4" round x 24" long sheet metal duct that has the long sides crimped but not connected. I plan to open this up flat and cut it into some strips (whatever width needed) to make the tent-in-a-vent mod. I figure at 24" in length, I'll have 4 shots to perfect it.

I can't do the mod today as it's sweltering today and the AC has not shut off in 4 hours. Next time I am at the trailer when we don't need the AC, I will go nuts with a marker, tin snips and a camera. Early on, I may tape mine in and if I decide to leave it, I may use pop-rivets or 1/4" hex head short screws.

Stay cool - now that you can!

Jim

Jim,
If you play with the deflector with the ac on, it will tell you when its happy. Just listen and feel the flow.
TimK

We put an extra vent in the living area on the door side. I also put the tent deflector in and had all the vent tunnels taped around the ac unit and found a difference in the air flow though out the coach. The ac also runs quiter in side the coach also. You will not believe you have the same ac unit on the roof. We have the 3400RL Bighorn. We have 100 degrees today and the temp. inside the coach is 74 degrees, not bad with the ceiling fan running. Evans & Lana

Jim ,, Hindsight being 20-20, I think 4 added registers instead of 3 would have been a good idea.. On my floorplan a fourth register could go nicely on the door side duct close to the door. That might pull a little cold air from the bathroom and add it to the kitchen area.. maybe next year...........

Guess we will have to do some modifications. We were at 78 yesterday and today on our BH, in nearly 100 degree temps. Did not feel bad inside, but sure got tired of hearing the AC run. Nan