Tired of the loud, annoying, Mach 8 AC units on your coach or RV? So were we but what could you do right? Wearing headphones all the time, while they worked well, quickly became an issue when you tried to talk. (Kidding of course about the headphones. After all, Brenda and I never talk.) Well, a company named Orbital Machine Works came out with a solution and it was not until recently I was made aware of it. They designed and sell the Mach 8 AC Hush Kit to make these noisy air conditioning units much better to live with. So, I bought one to try and then quickly bought two more!
The Mach 8 Hush Kit is more or less a simple controller that goes inside your air conditioning unit that will slow down the external condenser fan when you are running in LOW fan mode inside the motorhome. It is our guess that most of us run our units in LOW fan mode. We say this because, let’s face it, that squirrel cage fan inside really makes a lot of noise when running in HIGH mode. But what you might not realize, is the outside fan never changes in speed. Even when on low setting on the inside fan, the outside fan is always running at full speed!
When the Mach 8 Air-conditioners first came out they had a totally different fan in them. These fans were extremely noisy and the manufacturer had no choice but to come up with a new fan blade to quiet them down. In doing so, the new fan actually pulls more air than the AC actually needs to do it’s job. Which is actually a good thing because that means we can now also slow down the external condenser fan and thus greatly reduce the noise level. And that doesn’t mean just the outside noise, that also means the inside noise, as well there is less vibration and hum from the outside fan!
More or less there are two main parts of the kit, the controller and a new grille. The grille, as you will see, was also greatly needed as it has so much less resistance to the airflow resulting in lower noise.
It shocks me to say the least, that none of the engineers said.. “Hey, we can make this more quiet by reducing the air friction just by opening this up some.” Wait until you see the difference in the video.
Now pay attention as this is VERY important…You must have the correct compressor fan in your unit! You MUST HAVE the current D Series three bladed fan that became standard on the Mach 8 unit back around mid/late 2015 if I recall correctly. If you do not, you surely want to purchase the correct fan directly from your RV Manufacturer, a dealer/service center, or directly from Coleman/Airxcel. This is a MUST, you MUST have the correct fan, so get up on the roof and look inside the grille and see if you have a 3 bladed fan. If not, with a simple search and you can source the part. Sometimes Orbital Machine Works, the marker of the Hush Kit, will also have some in stock.
In any case, here is the video which is me talking about it and doing a full install. If you care to just see the results after all the work was done, you can jump to the 13:25 point in the video.
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The correct term for this fan is condensor fan. Not that it matters to anyone as I’m sure everyone knows what you are talking about here. I wonder what it is doing to the head pressure in the A/C system when it is on low speed and it is very hot outside? You see, if this pressure goes up, the rest of the pressures in the system go up and the overall cooling capacity becomes less.
Not sure where you are correcting me with “condenser fan” as it is part of the of the outside compressor system. :) As far as the pressures go, the unit running at the lower fan speed, with the new fan, still has the same air CFM as it did when it had the original 5 blade fan at a faster speed. The 3 bladed fan moves a lot more air than the original fan did and is why this is able to be done at all. It is still within original design specs.
Rick M is probably referring to this line: “slow down the external compressor fan”
The compressor doesn’t have a fan. The condensor, which exchanges heat so the coolant returns to a liquid from a gas in a single vapor compression cycle system.
We all know this crap. ;) ?
Semantics, but others might not know the correct terms or how it works.
I opted for the Mach 15. So the Mach 8 has two fans? One for the comp, err, condenser, and one for the evaporator?
Interesting, with its smaller footprint surprising they could fit two in there.
On the other Machs, they utilize a single motor with dual shaft.
And I’m jealous you have three units. There’s no pre-existing exhaust vent, or I’d add another over the bedroom on our Fleetwood Revolution. The pusher engine produces a lot of heat, you could add mist to the closet and steam your clothes probably on a trip.
Ah! I see, I understand. I was not sure what he was referring to as it more or less is is part of the same system and he is correct. But yes semantics for the most part. I modified the blog text to be correct as mentioned.
This may be a dumb question, but how does running the AC on auto affect the fan speeds and thus the noise level?
It does nothing. AUTO just allows you to manually turn on of off the inside fan and has nothing to do with the external fan which is what we are dealing with in this case. You can move it from AUTO to ON if you want to move air around. It will then run the inside fan at low or high setting. The controller is changing the speed of the outside fan based on the position of the FAN SPEED switch inside being on High or Low.
David, sure glad you tried this. Of all the mods I have made to my Bus, this is the one my DW REALLY LIKES. While the change in DB seems small it is really a big difference. We can now listen to the TV without increasing the volume or have a normal conversation. While we live in Alabama, we rarely have to increase the units from low to high. Cooling is about the same on low as it was before the mod.
Well you are the one I referenced in the video that alerted me to them. After giving it some thought for a time, I decided to give one a try and was impressed. :) Figured might as well do a video and let others know about it as it had been some time from the last time I did a good video seeing we had nothing really going on.
I’ve been considering this mod for my Phaeton, built in March of 2015.I generally run my units on “fan, high”. Does it still quite down the exterior noise while on high? The inside noise, in my opinion, isn’t too bad.
Not sure what was not clear about what this does, but it will not help at all if always running on high as the intent is to slow down the outside fan when running in low.
My first OOB video. The subtitles and editing were great. Fun, funny, and informative.
Thanks…Feel free to check out the others on our YouTube channel.
I dont see a mention of the price and do you feel a difference in the amount of air flow inside the coach before and after. Also do you find the low speed air flow good enough to cool the coach ?
I think you just needed a reason to use your sound pressure meter hehe. Us audio video philes hehe
Thanks good job
I listed the website for the pricing for I am not sure what each person would need so it was not mentioned, but linked to, on purpose. There are also price brakes based on how many kits you need. In my case, all three, was $325+ shipping. This only effect the OUTSIDE fan and thus has not effect on the inside one. I also did temp readings before and after taken right at the first out port of a ceiling duct hole, the temp coming out was the same on HIGH and LOW as it was before I put the kit in. I have had that meter from my audio video home cinema days of AVSForum. :)
Nice information you are sharing. The Mach 8 hush kit already I used in my RV air conditioner. It works perfectly.
Does anyone know if this mod is compatible with the heat pump version vs the stand alone ac unit?
The Mach 8’s we have, the ones done in this video, all have heat pumps. Not sure there is a non-heat pump version of the Mach 8. (Could be, don’t know. would think it would be a different model number.)
I just see everyone referencing the Mach 8 RV A/C Hush Kit, just makes me wonder…
the The RV A/C Silencer is the ticket to reduce the noise. I have installed mine and it works great. check them out.
Is this hush system compatible with any MACH models?
Hi Tony. You would want to contact the company that makes them for this one was made for the Mach 8 as it was so bad as you had seen in the video. They may have other kits.
On a new unit (2023) would this kit be needed or do you know if they have made the changes at the factory?
Sorry, no idea. Not even sure they are still using Mach 8’s. (Sorry for the delay.)