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2019 T@B 400 Bath Fan Replaced with MaxxFan 4301K that is too tall for the roof

I have commented on a couple of threads about the shortcomings of the bath fan in the 400. Mine is a 2019 model year with build date of Oct 2018. As there are a lot of variations in the builds I thought it might be helpful to show the steps to remove and replace the fan  in my model. I changed out to a basic Maxxfan I sourced from Camping World. Cost was about 130 dollars. Should have checked the dimensions as it did clearly state fan was for a minimum roof thickness of 2 inches. Other models with numbers above 5000 specify a minimum roof thickness  of 1 1/8 inches, which happens to be right where the T@B roof is. My bad. Even worse when I did not notice until the last step of installation!

I did find that the original fan is still made and can be found at RV outlets, if you are really attached to the current one.

First the removal of the old fan, a Dometic EZBreeze that came with the unit, was pretty straightforward on the inside.
The unit removes with 4 screws and the fan unit drops away from the trim ring. The trim ring then is held by 4 long screws and acts as a clamp to the roof vent. If you did want to replace this fan with the exact same all you would need to do is drop out the fan unit and replace with the new and you would not have to mess with anything on the roof. However you will see why a new fan is better further down.









My fan failed as have many others, due to the 4 plastic mounts shown below cracking and then allowing the small fan blades to jam.
Not to mention the little push OFF/ ON switch om the left which also fails. Once you see this you get motivated to put in something better because the design and materials of this fan are just awful. The little fan motor, though, is pretty sturdy and is going to make a nice little box fan project for the grandkids.



Now you have the unhappy task of removing the roof vent portion of the old fan. After I managed to carefully scrape away sealant I found 28 self tapping screws that have been put through the aluminum mounting frame, which is quite sturdy. All screws in mine were #2 Robertson square head. I reused many of these as they are so easy to put in and take out without the head stripping. This mounting frame is another example of good build quality from NuCamp creating a sturdy and long lasting little trailer.



To be clear on the wiring the black wire in my unit is the + POS lead, and the white wire is - NEG. Also note the aluminum skin and the interior thin veneer which is just below the aluminum framing. I was not able to measure but the mounting aluminum frame extends back at least 2 inches from the edge, giving you plenty of space to drill. I was concerned to think to measure the metal frame for mounting screws, and never occurred to measure the thickness of the roof. Don't be like me when you replace a fan.





Take a break now and get some solvent and elbow grease ready for cleaning the remaining sealant from the opening, which fortunately is a 14x14 inch standard opening. I picked denatured alcohol as it was compatible with the new fan plastic. Rub and pick and scrape and you will keep finding more. Then when you are tired enough you can quit.

The new fan I chose is a bit different from the fancy models as it has fan and mounting all as one piece. And it is taller than the more expensive models as well.
It exhausts and can run in ceiling fan mode with the cover closed. The instructions were good. You need butyl tape to cover the underside along where the screws penetrate and Dicor self leveling roof sealant. This was the step I should have sent the fan back for a swap to an appropriate unit but I forged ahead, happy that I knew what I was doing.





I had to prepare new crimp connectors for the fan to connect to the trailer, then center the fan in the opening and mark it so you can put it back after the butyl tape is applied, as you can't move it once it is down. Again the instructions remind you of these steps.

Remember that the frame around the opening is aluminum so drill appropriate pilot holes and avoid the power wires of course. Even with pilot holes a few screws were a bit reluctant to go in. Fortunately this replacement fan there are only 16 screws. Plus the fact that I screwed myself cause it was not coming back out at this point.





The inside and the trim ring on this fan are a bit different as well as the four flat head screws are going to hit the aluminum frame from below. The garnish ring needs to be trimmed per the instructions to make it fit flush. Somehow I fantasized that the trim ring would magically cover the fan that was now protruding down exactly 7/8 inch from the ceiling, just as Maxxfan had predicted.





The test of the fan prior to sealing it down was a pleasant surprise. I was used to our main cabin fan, which is a bit loud and has a whine, and the original bath fan, which was very loud and rattled incessantly. When I turned this Maxxfan on low speed, I had to look to ensure it was actually turning. I only noticed the slightest fan noise when I got to setting 3, and the air movement was markedly improved. It suddenly felt like it was worth the time and trouble as I could actually prop the bath door at night and leave this on and not even hear it operating. So that means I really like the fan. 






Now the trim is installed and the reality of the mistake starts to sink in. Thinking about the moisture from the shower. @Denny16 mentions that as well. He usually gets it right, so maybe we can just stop showers. No, the wife does not agree. After some good ideas from the forum (thanks @Sharon_is_SAM) I decide on a flexible trim/caulk strip that will seal the gap of about 1/4 inch and will require enough work, bending and straining to make the lesson stick as well as the trim hopefully does.

Now on to camping for a full week, which is always more fun. Good times to all who are getting to go to UCamp22! We hope to get up there some year.

2019  T@B400 Boondock Lite "Todd"

2016 Toyota Tundra 5.7 Crew Cab

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    Denny16Denny16 Member Posts: 5,431
    The trim caulk Sharon suggested may do the trick, doesn’t tanks much pressure, just a good seal.
     Cheers 
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    peterjoce400peterjoce400 Member Posts: 51
    Thanks for sharing. Our bath fan is identical Dometic and we had the motor rust out and switch fail. I had thought of the Max and would never have thought of the roof thickness.  I did replace the motor (which was easy but of course the shaft for the blades was the wrong size!!) and the switch to waterproof toggle.  The plastic shafts for the screws cracked so some tape and epoxy and all glued back together.  Next time I will go your route.  
    Hans Peter,  Nanaimo, Vancouver Island
    2019 T@B400 Rogue
    2012 VW Touareg 3.0 TDI
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    MuttonChopsMuttonChops Member Posts: 1,596
    Interesting post, thank you.

    The yr-2022 400's (do not know about '20, '21) have a round MaxxFan Dome Plus (with LED lighting).

    Based on the literature the Dome Plus might be an ideal fan for the 400 Bath.

    '18 320 Spitched axle, 3020HE; PNW based
    TV: '17 Colorado V6 Z71 4x4, Tow Package, GM Brake Controller
    Adventures:  51   Nights:  322  Towing Miles 41,200+
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    Except if you have a 2018-2021 you have a big square hole in the roof so you would have to stick with the same shape/dimension. 

    The round fan is new to the 2022 model. I really like it so far except it doesn't have a reverse option which I used to help dry things out after a shower. 
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    Denny16Denny16 Member Posts: 5,431
    I agree TabbyShack, the new round fan is nice and compact, and is being used on a lot of RVs in Europe, but it lacks the reverse air in mode.  We use this air in mode to also fry out the shower after taking a shower.  Also, we discovered, using the reverse air downdraft mode keeps the shower curtain from sticking to you whilst showering.  Afterwards, we run the fan in it normal air out mode to clear out the moisture, then put it back into Air In mode to help dry the shower.  Works great. So far no issues with the original fan in our 2918 TaB400.
     Cheers 
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    ColoradoJonColoradoJon Member Posts: 415
    When I installed my MaxxFan I built a simple, square shim from 1" pine and mounted it on the inside ceiling. This allowed the fan flange to sit below the ceiling by 3/4".
    Jon & Angela | Florissant Colorado | 2017 Outback S
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    Denny16Denny16 Member Posts: 5,431
    That was the solution I was suggesting at the start of this discussion.  I think this is the best option to solve the issue.  Paint the pine or ? trim white, mount the fan and Bob’s your uncle... 
    cheers 
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    qhumberdqhumberd Member Posts: 471
    As always my appreciation to this forum for the help and ideas. @Denny16 @ColoradoJon and @Sharon_is_SAM allowed me to demonstrate my shortcomings while providing viable solutions when my first reaction was just anger and frustration. Thanks all!

    2019  T@B400 Boondock Lite "Todd"

    2016 Toyota Tundra 5.7 Crew Cab
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    qhumberdqhumberd Member Posts: 471
    Final picture showing InstaTrim 3/4 inch molding to seal gap. Looks ok and is well sealed. Feels like I got off with just a warning this time 😊 Happy Camping










    2019  T@B400 Boondock Lite "Todd"

    2016 Toyota Tundra 5.7 Crew Cab
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    Denny16Denny16 Member Posts: 5,431
    It came out nice, now it’s time to go camping!  B)
     cheers 
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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    qhumberdqhumberd Member Posts: 471
    We have a week with our grandkids coming up, and they helped take the old bath fan out and helped build this 12V box fan for the table from scrap materials. Great for white noise and moves a lot of air. Also great to show them not just to throw everything out. 




    2019  T@B400 Boondock Lite "Todd"

    2016 Toyota Tundra 5.7 Crew Cab
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    Denny16Denny16 Member Posts: 5,431
    edited July 2022
    Nice utilization, and the fan continues to be useful.  The youths got some carpentry experience in too, and the box came out nice.
     Cheers 
    2018 TaB400 Custom Boondock,  Jeep Gladiator truck, Northern California Coast.
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