Hey Keystone found your saw dust, also A/C Mod. - Montana Owners Club

scott-pati · 08-31-2016, 11:03 AM

UPDATE - DW and I have been pleased with the added insulation to our A/C units. It really has helped keeping our Monty cooler without a doubt.

Watch for another A/C mod post in the coming weeks. This mod made a bigger change in cooling and increased air flow!

Decided the other day to take a closer look into our A/C cooling issues. I did this to my unit and a friend of mine on this forum, also a 2014 Montana. I already went through my ducts and pulled them apart to see if they needed to be trimmed down to be flush with the actual ducting in the ceiling as written up by others. I was surprised to find my vent covers were only sticking up into the duct by a 1/8”, unlike others have posted being an inch into the duct. Maybe it has something to do with the newer build dates. Mine was built in August of 2013.

Any way I headed to the roof. I removed the top cover of the rear A/C unit first, and then removed the 8 screws that covers the evaporator. Look at the pictures below. He’s your saw dust Keystone! Remember, that 2 images are my unit and the other 2 are my friends.

We brought up a vacuum to remove the saw dust and cleaned the evaporator as well. We repeated this for the front A/C unit too. We found no saw dust in the front unit. We put everything back together and added extra insulation around the evaporators using foil tape NOT DUCT TAPE to secure everything together, in both units as you can see in the last photo.

Before doing any of the above work we took vent temps using my IR in both of our units. Our units had been running all day and both units were in the sun. There was only a 2-3 degree difference between our units. Those temps read around 52-55 degrees. After adding the insulation our temps dropped down by 6 degrees to around 46-49 degrees at the vents.

Another interesting find was if you had the rear A/C running and the front running on fan only, the duct temps showed a 20 degree difference from reading the rear ducts and working my way forward to the front ducts.

If I kept the rear A/C unit running and turned off the front unit (no Fan or A/C), then there was only a 6-7 degree difference. Reading the rear A/C ducts closest to the evaporator I would get that 46-49 degree temps. The readings would get warmer as I went to the front.

In closing to get the maximum out of your units, they must both be running on A/C mode. The duct readings only varied by 2-3 degrees this way. Hope this helps...

Below you can see the saw dust on top of the evaporator and at the base of the unit. There's no telling how much was in the evaporator fins.

Below added extra insulation on both A/C units.

Former StClairSailor · 08-31-2016, 12:05 PM

Great photos! That's enough motivation for me to check out my rig. Thanks.

jameswbarton · 08-31-2016, 12:56 PM

A real Quality Product We have purchased! I wonder if your front AC was added later thus no sawdust? BTW if the collars are in the duct area at all you should trim them. An 8th of an inch will cause the air to hit the vent and create an eddy current resistance. It appears they ordered a bunch of wrong length collars from the vent mfr and used them instead of returning them After all a Quality Inspector would not notice them once they were in the ceiling.

richfaa · 08-31-2016, 01:12 PM

Just went out to the garbage and measured the collars on the vent covers we took out of our2013 3402 big sky. They measured 1 3/4 inches so they were at least one inch or more into the duct. There was so much sawdust in some of our ceiling lights that they were dim.I was surprised they did not catch fire.

When the mobile techs removed our fridge when it failed to replace the cooling unit enough sawdust came out that we could have used it as kindling to start a fire.

We had the same issue in our 1995 Coachman and our 1996 Terry and our 2006 Montana 3400 What are they supposed to do with all that sawdust.

jameswbarton · 08-31-2016, 01:28 PM

I had to cut exactly an inch off of mine to be flush.

bigskyjimmy · 08-31-2016, 01:28 PM

Nice Write-up and I checked mine out just now and my 2015 Already has a big molded styrofoam piece around the Evaporator on both my A/C's... Just you're Luck ya missed it by one year

although that is a nice cheap improvement

I did not see any sawdust on mine I guess the "Fine Amish Craftsmen" gave mine the special treatment

Goin 4 Broke · 08-31-2016, 05:49 PM

Thanks for the great write up Scott. How easy is it to remove the shroud/covers? Are they just held on with screws? Also how did you determine where and how much to insulate? I am headed up on the roof in the next day or two for my first maintenance of the A/C units so your postwar very timely!

sambam · 08-31-2016, 07:13 PM

I'm sure you all know this, but be on guard for wasps under those covers..

WeBeFulltime · 09-01-2016, 01:36 AM

Odd, but I haven't found any sawdust anywhere on our 2012 model and I have been in all nooks and crannies in the five years we have had it. I have also checked the inside a/c discharge registers and they are not too long like they were on our 2008 Montana. I had to trim all of them on the 2008.

scott-pati · 09-01-2016, 03:12 AM

Quote:

quote:Originally posted by bigskyjimmy

Nice Write-up and I checked mine out just now and my 2015 Already has a big molded styrofoam piece around the Evaporator on both my A/C's... Just you're Luck ya missed it by one year

although that is a nice cheap improvement

I did not see any sawdust on mine I guess the "Fine Amish Craftsmen" gave mine the special treatment

The rear A/C had dense soft foam that one side was sticky and was placed on and around the metal evaporator section and the front as mentioned, I also had the molded Styrofoam fitted over the evaporator cover too. But some how mine had a hole in the middle of it. Perhaps from the outer cover rubbing on it? Who knows... Plus the molded Styrofoam did not cover the entire evaporator housing down to the base. They were two different design units, which is normal. The rear being 15k btu and the front 13.5k btu.

Any way I still covered them up with extra insulation.

scott-pati · 09-01-2016, 03:22 AM

Quote:

quote:Originally posted by Goin 4 Broke

Thanks for the great write up Scott. How easy is it to remove the shroud/covers? Are they just held on with screws? Also how did you determine where and how much to insulate? I am headed up on the roof in the next day or two for my first maintenance of the A/C units so your postwar very timely!

The rear unit had 6 or 8 screws and the front had 4 screws. All were the standard #2 phillips.

I bought Duct insulation, I needed 2 rolls and 1 roll of foil tape.
click here to see the duct insulation I bought. I just used one layer to wrap around and over the evaporator sections covering over the existing foam pieces to give it more insulating power.

scott-pati · 09-01-2016, 03:28 AM

There's no telling how much saw dust was really up there when the unit was brand new. I will have had my unit almost 3 years and about twenty trip of shaking and bouncing around on the highway. I'm sure there was a lot more of it.

Can you see me now when I buy another unit, the first thing I'll be up on the roof on the dealers lot taking apart the A/C looking for saw dust. LOL

scott-pati · 09-01-2016, 03:34 AM

Quote:

quote:Originally posted by richfaa

Just went out to the garbage and measured the collars on the vent covers we took out of our2013 3402 big sky. They measured 1 3/4 inches so they were at least one inch or more into the duct. There was so much sawdust in some of our ceiling lights that they were dim.I was surprised they did not catch fire.

When the mobile techs removed our fridge when it failed to replace the cooling unit enough sawdust came out that we could have used it as kindling to start a fire.

We had the same issue in our 1995 Coachman and our 1996 Terry and our 2006 Montana 3400

What are they supposed to do with all that sawdust.

Sell it as Hampster bedding!

Fire5er · 09-01-2016, 05:01 AM

Thanks for the great write up and pictures...the picture really make the difference in understanding the issues we all have had with sawdust in the A/C vent system.

psomers · 09-01-2016, 06:52 AM

Hi Scott. How do you suppose saw dust got in the evaporator. Was it sucked in from the AC cut out? Was the saw dust mostly on the input side of evaporator or output?

scott-pati · 09-01-2016, 08:56 AM

Quote:

quote:Originally posted by psomers

Hi Scott. How do you suppose saw dust got in the evaporator. Was it sucked in from the AC cut out? Was the saw dust mostly on the input side of evaporator or output?

Hi Paul, there's no telling how it gets there. My guess it's properly laying on the roof before they install the EDPM roof material and it gets kicked and shoved around while the EDPM is installed. If that's the case then they truly are in a hurry to button up the RV's and move on. NO FURTHER COMMENT for fear of getting shut down for fowl language that may have followed...... LOL

To answer your other question, I did not see very much saw dust that may have gotten through the evaporator. That has probably been blown out through the ducts a long time ago.

scott-pati · 09-01-2016, 08:58 AM

Quote:

quote:Originally posted by Fire5er

Thanks for the great write up and pictures...the picture really make the difference in understanding the issues we all have had with sawdust in the A/C vent system.

Your very welcome to you and others that have had kind words for my write up!!!

Just trying to understand how and why these RV's are put together.

Fire5er · 09-02-2016, 07:31 AM

Those that don't get into the areas that are out of sight will never know what is lurking to cause them problems down the road. Better to be proactive than reactive. I couldn't believe all the issues I found behind the basement walls of our new BS. Again great job and post. This is what is so great about this forum.

jameswbarton · 09-02-2016, 09:08 AM

Fire5er,
Ok what do I need to look for in my new HC basement?

scott-pati · 09-03-2016, 03:27 AM

Quote:

quote:Originally posted by jameswbarton

Fire5er,
Ok what do I need to look for in my new HC basement?

Are you sure you want to venture in the basement? There are evil things lurking down there.

wires, and hoses swinging freely in the cool damp basement. WAIT what is that moving in the corner.... a snake?

Oh, it's just a disconnected HVAC hose swinging in the cool night air.

Wait the floor feels funny... I think it's moving!

Oh, it's just more saw dust! Lots of saw dust!

Why is it so damp down here, this place gives me the creeps! You look to your right and find a few loose plumbing fittings.

Okay, that's enough for me, I'm outta here!!!

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