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Old 06-26-2022, 09:17 PM   #1
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Join Date: Jun 2022
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M.O.C. #31245
Coleman Mach Q /AC system

New to the group and like most, interested in discussion topics to improve or better understand certain functions. My 2022 Montana 3813MS has two Coleman Mach Q air conditioning units with the blade (vent) system. Forum member Foldbak started a discussion in January about the lack of air flow with the blade vents. I second his concern!
My units also have the Coleman Mach Plenum installed and I spent this past weekend working to improve the flow. Most ceiling vents pop right off however I have was unable or failed to use enough force to remove the bladed vent. Primary intent was to inspect and seal duct (as needed) to prevent cool air loss into ceiling. I then opened the filter cover —- to my surprise, there was no foam or other plenum separating the intake and return. The Mach plenum is a hard plastic box (similar to the RV Airflow box) that covers the return. The intake side was fully exposed (as were wiring) and I was loosing a lot of cooled air up the intake . I used aluminum HVAC tape to seal it as best I could. I have (and used) the RV Airflow system in my other unit and want to install in the living area unit but don’t see how that is possible without replacing the plenum unit since it seals to.ceiling. Anyone here have this type plenum and replaced it or somehow improved air flow function? Attached pics of unit
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Old 06-27-2022, 08:32 AM   #2
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M.O.C. #30417
I've yet to tackle this one but it's on my list. There is a lot of good stuff on you tube and I don't think it matters what unit you have. The objective is the same. Let us know what you find and do.
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Old 06-27-2022, 12:29 PM   #3
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M.O.C. #26926
FYI - "Intake and return" are the same. "Supply" is the forced air. Intake side of the unit is the return air which then gets conditioned and output/supply comes out of the registers.
Rip & Beth
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Old 06-27-2022, 12:36 PM   #4
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M.O.C. #30294
I'm interested in this as well and will be following along to see what you do. I had Dometic ACs on my 2014 - 3850FL. RV Airflow didn't make a kit for the AC on my rig so I made one myself using 1in foam board, reflectix and HVAC tape. That mod cut the noise level in the kitchen by 50% and made a significant difference in the airflow through the duct system.

I will say that the Coleman units are very quiet and I get a consistent 20 degree temp drop at the "blade" vent compared to the return air intake on the AC. One other thing that many people don't notice is the amount of airflow you get when both AC units are running vs only one unit. Since the duct system runs through the entire coach, a single AC running is trying to cool everything and is pushing air from one end of the trailer to the other to do that.
Clark & Peggy
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Old 07-15-2022, 08:33 AM   #5
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Join Date: Jan 2014
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M.O.C. #13970
These vents will pop out by pulling hard but once you get one down you'll see there are 2 tabs that can be pushed in. I have a 3813MS also, I have contemplated moving my bedroom a/c to the kitchen area. I'm in Florida and my bedroom will stay ice cold and the living / kitchen area will barely maintain 80 degrees. I only run the living room a/c at night and it will maintain 71 degrees with no problem. I end up running the rear a/c at 80 and the bedroom at 70 with the fan on high. If I don't move the unit I'll put a 3rd a/c in as soon as I have time. I have checked all of the ducting and made sure the return and supply air are separated and I've put Reflectix on some of the windows.
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