Air Conditioner Issues

[Bourbon County]

Originally Posted by twindman

Tho laser thermometers are for surface temps, not air; if you point it at something solid in the exit vent, you ARE measuring surface temps. The aid should cool the vent grate to the same temp as the air.

That can be accurate in some cases, not this one. If the surface exposed to the cooled air has a high ratio of thermal conductivity you would be accurate. Materials like copper, aluminum, and most metals have a very high ratio of thermal conductivity and would in time reach near equilibrium with the supply air. These diffusers are plastic which has among the lowest ratios of thermal conductivity of all materials, would likely never reach equilibrium.

The point I've been trying to make since the beginning of this thread is that a cheap BBQ thermometer will give some very accurate results in a very short time frame.

[LJSantore]

https://www.youtube.com/watch?v=yasE7IFnbNg

this Explains the way to get max air from the vents. the Word Blade should be facing the AC unit. also you can do a simple Mod to get more flow here is the link for that https://rvairflow.com/

[Mikendebbie]

The RVAirflow systems do not apply to ducted system. I do not have access to either of my ACs from inside the coach. It works for various systems that have ceiling access like the one pictured below.

[Bourbon County]

Originally Posted by LJSantore

this Explains the way to get max air from the vents. the Word Blade should be facing the AC unit. also you can do a simple Mod to get more flow here is the link for that https://rvairflow.com/

In theory that sounds right. With 2 units and the Keystone racetrack duct system, which unit is supplying air to that vent, especially the ones halfway between the units? The answer is both. The Colemans use the same size blower on both the 15K and 13.5K units.

I spent a lot of time measuring airflow at individual vents with an anemometer and a homemade capture hood. I was able to finally adjust airflow down at the vents mid coach and pushed more air to either end. My unit is front bed, rear living and that's where I wanted the most. I do have to leave both units running the fan in manual high to keep the same balance when the compressor has cycled off on either unit.

I agree with Mike about the RVairflow product, not needed in a ducted system. The new Colemans supposedly have an OEM version anyway. Couple that with the price they ask for a piece of molded foam and the trouble or cost of lifting the unit from the roof to install, I don't see the value.

[Daryles]

If you search Air Conditioning, you will find a bunch of threads on this topic. Many ideas repeated here.
I would only add remove your return filters.
Tape up any gaps going into the attic.
Cut back any protrusions in the ceiling restricting return flow.
After all that, one of our members removed the AC unit on the roof and discovered it was not centered correctly over the cut out holes allowing cold air to go into the return air duct.

[GetGone]

Originally Posted by Bourbon County

If you have tested and confirmed the units are actually cooling, the next step is to check airflow........

Okay, I went to home depot and purchased the BBQ thermometer. When used to test the air temp in the vents it was 55°. I had the rigs thermostat set to 68° During the heat of the day the thermostat read between 78° and 80°. The outside temperature was in the mid 90s.

Without the blade vent covers in place the air flow is much better. One vent in particular is noticeably better than the others.

So there's the reading that you suggested I take. I'm interested in the $100 fix you mentioned in one of your post. I sent you a DM with my email address.

I truly appreciate the info and thoughts that you and everyone else has offered.

Scott

[VagabondLove]

We ended up adding two additional intake vents and propped the intake ducts open to allow more air into the system. Improvement found here https://www.montanaowners.com/forums...ad.php?t=83870

[Mikelff]

Originally Posted by GetGone

Hello again. We have a brand new 2023 Montana 3793RD. It presently has 2 Coleman Mach Q A.C.'s which are ducted. This is our first camper with ducted A.C. Our others had the roof mounted units that were so loud you could barely carry on a conversation. However, they definitely blew out the cold air!! My concern with my new unit is the AC's aren't working efficiently. The camper is out of direct sunlight parked in a pole barn. Yesterday I set the thermostat to 68° Hi-Cool Auto for the den AC. After running for over 2 hours the thermostat still read 78° which is the same as when I turned it on. The camper really didn't feel any cooler than it did before I turned on the AC. When pointing a laser thermometer directly into a vent it reads 68° but when I move the beam over a couple of inches it reads 77°. When I put my hand directly up to the vent the air that is coming out is definitely cool but there is very little air flow coming out of the vent. All the vents are like this. I closed up the bathroom and bedroom to reduce the area being cooled. Is this normal for a ducted type AC? Should I go ahead and add the 3rd AC in the kitchen? I'm all ears. I look forward to reading your thoughts and hopefully solutions. Thank you all for your information.

I would also recommend checking all your vents to make sure they are sealed up and no gaps where the vents attach to the ducts. Many folks have found gaps that needed taping with the aluminum duct tape. Some were barely connected, so much of the cold air was going into the attic. Blocking your furnace cold air returns and heating vents makes a big difference. Its amazing how much hot air come up through the floor vents and furnace air returns. Depending on how hot the rig is when you start up it can take a couple hours to cool down.

[skippydoo]

Take it back to the dealer and have them make it right. Do NOT allow them to tell you it is in full working order. Because it is not and they know it.

We are in the Carolinas---only travel TO hot areas.
Our rig (2019 331rl--37 1/2 feet long'ish with 2 ac units.) temp in main cabin and bedroom is usually set on 62' and it IS freezing inside our rig. Sometimes we are so cold that we turn temps UP to 65, 66m just to warm UP. Then down it goes again to 62.

I will say this, so you know, do NOT to listen to service OR sales OR the dealer who tells you "if it 90 outside your lucky to get inside temps 10 to 15 degrees cooler inside". Hog wash.
Also,
You should not have to close any doors to help maintain a temp in the main cabin and bedroom. Our bathroom has 1 vent and it is very, very cold in there.

Hate to say this but our motto has been over the years if, IF you cant hear the AC, it is not working right.

You should be under warranty. Remember do not allow them to tell you the ac is running normally. Even IF you decide to add a third ac, it will not fix the problem you have with the two current units. Your units should cool down temps down a lot more than you are getting.

Please come back to us and give us an update, ok? Good Luck.

[Toma-in-TX]

Hi, what did you find to replace the vents? I’ve searched and can’t find the right size to snap into the collar in the ceiling. I agree, the Blade diffusers are awful.

[Foldbak]

Originally Posted by Toma-in-TX

Hi, what did you find to replace the vents? I’ve searched and can’t find the right size to snap into the collar in the ceiling. I agree, the Blade diffusers are awful.

This is what I used. It snaps into the collar. The screws show a bit so I painted them white.



https://www.amazon.com/dp/B082FYRYBH...roduct_details

[Bourbon County]

Originally Posted by Toma-in-TX

Hi, what did you find to replace the vents? I’ve searched and can’t find the right size to snap into the collar in the ceiling. I agree, the Blade diffusers are awful.

I bought the Valterra A10-3359VP from etrailer.com for everywhere except bath where I used a Valterra A10-3354VP. You'll find there aren't a lot of choices on the market. They are larger diameter which is a really good thing and you have to cut the hole in the ceiling out a little. I used an oscillating saw which worked very good.

With the racetrack duct system, the highest air pressure is in the middle of the coach halfway between the 2 units. I ended up closing the vents off quite a bit on those. The A10-3354VP is an old school spin to adjust model; the bath is a very small space and doesn't need very much airflow. If you're going to be in there for an extended length of time it's easy to reach and open it up a little.

Since the A10-3359VP is directional, try to point them away from a return as much as possible to prevent an air "short circuit". When installing the sleeve inserts, carefully check the height, they need to be flush with the duct insulation or slightly below; trim them down if needed.

[skippydoo]

Valterra A/C Vent Spaceport 4" White

Hi, we purchased a bunch of these on Amazon to replace the vents back in 2020. Amazon sells them for abt 6.50 each.

https://www.amazon.com/Valterra-A103...%2C164&sr=8-19

[GetGone]

Originally Posted by Toma-in-TX

Hi, what did you find to replace the vents? I’ve searched and can’t find the right size to snap into the collar in the ceiling. I agree, the Blade diffusers are awful.

Sent you a PM

[2 Yoopers]

Originally Posted by VagabondLove

We ended up adding two additional intake vents and propped the intake ducts open to allow more air into the system. Improvement found here https://www.montanaowners.com/forums...ad.php?t=83870

I did all the mods, larger spaceport vents, and tubing to open the ducts when I owned my 2015 3711fL but it was still not putting out very much air.
I agree the restrictive air returns are a huge part of the problem, as well as to few vents in the unit.
My current motorhome has 16 vents in its 42’ length and simular Dometic units that I had on my Montana, that only had 8 vents I believe. With 1 unit running, I can feel good airflow at the opposite end of the coach, unlike the Montana.
My air intakes are open. Yes they are slightly louder that the ducted intakes, but the air flow increase is huge.
Loved our Montana, but the air conditioning not so much.

[LJSantore]

We Always Run A Dehumidifier. Getting humidity out is the First Job of the Air Conditioner. When not on the road I let it drain into the kitchen sink.

[VagabondLove]

Originally Posted by Toma-in-TX

Hi, what did you find to replace the vents? I’ve searched and can’t find the right size to snap into the collar in the ceiling. I agree, the Blade diffusers are awful.

I ended up using an orbital saw to cut away a few vanes (for less restriction while keeping a few vanes for direction control) and to shorten the upstream side of the vent (so it acts like an air scoop)…

[Bourbon County]

Here's a procedure from Airxcel (Coleman-Mach) for evaluating AC performance. Note that the current measurements are for the compressor only, not including fan(s). That means a trip to the roof and removing the shroud if you have ducted units.


file:///C:/Users/Ed/Downloads/Airxcel%20Evaluating%20Air%20Conditio%20-%20Airxcel.pdf

[SonnyP3]

Originally Posted by bshgto

all a/c the fixes are useless. Go to walmart and buy 2 6000- btu window a/c`s and put one in the bed room window and one in the living room window and remove while traveling.. That`s the only fix that will bring the temps down. The temps out of the window a/c`s is far lower than the first vent from the ceiling units. A third a/c is useless because you can`t run all 3 time a time anyway unless you have electrical knowledge to defeat the control box. Compaire costs and hassle.

I have run all three of my A/C’s since day one. I own a 2023 3763BP. As long as I have shore power, I run all three day and night.

[Sr. Oso]

Reading this thread with interest. Has anyone tried the product from KoolRV
https://koolrv.com/?