Finally! I Got my Mach 8 Plus Cub Air Conditioner issue Figured Out!

[m1mbeverly]

I bought from the factory, over 3 years ago a brand new 2016 Casita Spirit. And today have fallen in love with it again! I hope this story is useful to those of you that can’t seem to get their Mach 8 to make their trailer cool as a meat locker! “For those of you that don’t like to read long Posts, the solution for me was a new 93303411 Thermostat Heat/Cool.” For the rest, here is my story…. We are from Northeast Texas where it is always hot and humid with little wind. In the summer 98 degrees and 90 percent humidity is typical. In this type of weather for the first 6 months of adventures in the Casita we slept like babies in our cold trailer under heavy blankets. Then in early spring we went to the Texas Panhandle, New Mexico and Colorado. On this trip we couldn’t get any cooler than 73 degrees in the Trailer running it day and night in the shade. The air conditioner was still under warranty, so I took it to the local RV repair shop and had them look at it. I said, “I thought it was the thermostat because it would get cold coming out of the AC but the compressor wouldn’t stay on long enough to cool things down. 5 weeks later after several calls it was fixed and ready. They had to replace the whole unit and it wasn’t the thermostat. So off we go on another adventure after the warranty ran out. Started having similar issues. We read on this and other websites humidity was most likely the issue. We bought a large dehumidifier that just fit under our dining table and that helped. We got our windows tinted that helped. I made bubble wrap window insulation that helped but still just not like it used to be. All this because I was told by professionals the air conditioner was fixed.
I happened upon a Youtube video of a guy that showed how to adjust the thermostat by turning an adjustment screw on the thermostat. I had no luck with this. The air conditioner compressor still wouldn’t stay on long enough to keep the trailer cool. The compressor would stay on less than 2 minutes cool down to about 72 then not kick back on until the temp would get to about 78 before kicking back on. This temperature reading I took right next to the thermostat probe. Thus I finally decided to try a new thermostat. So I got on Amazon and ordered a new 93303411 thermostat heat/cool $38. While ordering it I saw a Coleman 9430D7153 Adb Deluxe Chillgrille $88 and liked it because it had 2 air vents that blow directly down and thought this would also help the cooling process. Once receiving these two items, to my delight, I found the Chillgrille came with a complete control unit which included a new thermostat. I replaced my old Airxcel ceiling control unit with the new Coleman Deluxe. (FYI there are only 8 small screws that hold the units to the ceiling, all holes line up perfectly. EZ install. Don’t forget to throw the breaker before rewiring the electric connections.) I then turned the breaker back on and turned on the Air Conditioner and in a matter of minutes it was 69 degrees in the trailer. The outside temp was 90 and 89 percent humidity. The compressor now stays on until temp as cool as I want it in the trailer. What a great day for me! I hope this story helps someone….

P.S. I kept the 93303411 Thermostat Heat/Cool in case this happens again. Can't find these at Walmart and when Air Conditioner out Mama Ain't Happy!

[Roamer]

Is what you did was to put a thermostat away from the ceiling unit, or just replace the parts inside the ceiling assembly?

[m1mbeverly]

Yes I just replaced the existing thermostat didn't modify to an external. I have read so many other peoples comments with the same issue I had , but no one had advice to change the thermostat. It is relatively easy to change except for the short air conditioner conduit that has to be removed...i just used aluminum conduit tape to seal it back in place. There is a YouTube video of a guy adjusting his thermostat to what he says will be cooler by disassembling the air conditioner and retrieving the thermostat. This is what I watched to learn how to. Hope this helps...

[Roamer]

I have a Mach 8 coming in tomorrow. I have the ceiling assembly already, and the thermostat is with this….

I ask because I may have the same issue, or is it just some Mach 8's?

I not quite follow your issues. Was your original thermostat getting too cold too soon while the compressor was on and then turn off the compressor before the room got cold?
Thermostat should be in the return air line, so how was it getting cold enough to signal that the room was cold and to turn off? Was outgoing air entering the return line too quick?

My controls have a temp sensor, which is a long copper wire about 6 inches long, that is supposed to be adjusted so it is in the return air flow. Could it be your temp sensor was not positioned? Maybe it was leaning against the wall next to the cold air duct???

If the return air is warm I don't see how it tells the controls to shut off the compressor. This is why I am confused…

[m1mbeverly]

The probe was in the return air, yes. While diagnosing the issue I used a cooking thermometer placed next to the thermostat temp probe to record the temps when the compressor would kick on and off. The thermostat and probe are both located on the inside unit on my air conditioner. Set at max cool the compressor would at about 79 degrees on and at about 73 degrees kick off. So the lowest temp a could get was 73 then the temp in the trailer would have to get up to 79 before the compressor would kick back on and only cool it down to 73. Once I replaced the thermostat and set it at max cool I got temps going down in the 60s and the compressor would kick off and on maintaining the 60s. The thermostat was now able to maintain temps where I wanted without such large temp fluctuations between compressor kicking on and off like it is supposed to.

[Roamer]

I just installed my Mach 8. I put a thermometer (ceiling assembly shroud not attached yet) in the cool air flow and it got down to 54 degrees when I took it out, seemed to be stable. Fan on low. Is a frig thermometer.
I have it in cabin now, temp is about 64 when I turned it off. So, 28 degree drop on low fan speed without the shroud. 100 deg might give me 72? Im not sure if the compressor was cycling

I have the fan speed on Low since that will produce a lower temp at the output opening (for thermometer). Low is much quieter than high, but without the shroud muffling noise is louder anyway… The noise level is just fine with me.

Hopefully no issues with mine…
i was careful how I placed the thermostat probe.

92-94 degrees, in full sun, the back corner is nearest the sun so condenser is in the sun, 900 feet elevation.

It feels nice in the cabin, though without the shroud air is not directed to the front upper bunk.

I have Coleman 9430D715 Air Conditioner Ceiling Assembly,

[rdickens]

So, was the solution really just to replace the inside unit with the Coleman 9430D7153 Adb Deluxe Chillgrille with its integrated new thermostat?
(I think you said that you kept the new separate thermostat that you had ordered as a backup?)

Thanks for posting this solution!

Ray

[Roamer]

rdickens, you quoted my part #. I am not OP and do not have cooling issues; I just have the same AC, and reading this post as you are. The OP used part 9430D7153. My AC works perfectly fine for the two hours I ran it so far…My ceiling assembly was the cheapest I could find on ebay. I paid $85 (I think normal retail around $120).

It sounds like OP had personal problems with his particular thermostat unrelated to the roof unit. Maybe he could have just replaced his 93303411 with a new 93303411 and had success. I am unclear what exactly his issues were being caused by…

[m1mbeverly]

Rdickens,
All I needed to fix my air conditioner issue was to replace the thermostat. But I bought the new chillgrille because it has vents that blow directly in the middle of the unit, the chillgrille comes with a thermostat already built in. And I bought the replacement thermostat to have for a quick if on the road. So if your are needing to replace your thermostat just get the 93303411 for about $37. But if you want a the extra blower vents buy the chillgrille for about $85 which includes a new thermostat.

[rdickens]

Thanks Mike!

I don't have a Mach 8 Cub Plus yet, but I've been seriously looking at one.
(We've been using a 5,000 BUT Frigidaire window AC, but it is more work to install when we stop and has some potential for leaking in a really heavy rain.)

Sounds like the Chill Grill might be a good top unit to order for the 8 Cub Plus.

Seems like I heard that Little house Customs was now recommending the
Mach 1 Power Saver now?
(IIRC it is taller and more BTUs than the 8 Cub Plus.)

Thanks again!

Ray

[Roamer]

maybe off topic…

I removed the internal louver that directs air up or down and also closes the output vent. It made extra wind noise and I figure I will never close the vent on that side, its the bed side.

It is much quieter now. It increased airflow slightly also, so cooling an in-perceivable amount better.

For fibergalss RVs the 9200 can turn it into a meat locker pretty quick.