Bedroom AC question

[John McLean]

Why is it that the bedroom AC unit in our new 2019 HM331RL will come on, run for maybe a minute, shut off briefly, come back on, run for maybe a minute, shut off briefly, come back on for a longer period, shut off, come back on and then repeat the pattern over and over?

[Mosnowman]

I was just getting ready to ask this same question’ 2018 3721RL has the same issue. I don’t have an answer but thanks for starting this thread!

[MidMOTraveler]

You need to be running on High
If set to Auto the fan speed keeps changing.
Also if on Auto in high humidity it’s likely to freeze up due to low air flow.

[John McLean]

Ah. Thanks. Will give that a try and report back.

John

[John McLean]

Just checked my control in both the bedroom and living area. There is no’High’ setting. It is ‘Auto’ with a snowflake. Looking for clarification.

[Skw774]

Set the fan on high before you get to the snow flake. Use the mode button and the up/down to accomplish this.

[mtlakejim]

Originally Posted by John McLean

Just checked my control in both the bedroom and living area. There is no’High’ setting. It is ‘Auto’ with a snowflake. Looking for clarification.

From the snowflake screen, hit mode and it will go thru heat pump then furnace then off and then to a FAN speed screen where you can change the settings with the arrow keys to low/high/auto. You want to be on high fan.

Once you set the fan to high then hit the mode button once more and you will be back to the AC or as you call it "snowflake" screen.

Your compressor will still turn on and off with the set temp. but it will run smoother with the increased and constant air flow.

There have been some other folks that have suggested that the thermostats sitting on walls with large holes behind them may be influenced by the trapped air in the wall. Don't know if there is any truth to that but might be something else to consider.....

[Daryles]

Ah, I vaguely remember this from our orientation. Fan speed on high not auto.

[twindman]

My previous Montana had the bathroom light switch right directly behind the thermostat. When the light was on the switch would get warm and messed up the thermostat. At least that is what my old memory says.

[mfrey3]

While setting the fan on High stops the cycling, it also means the fan runs constantly. This doesn’t seem like an acceptable solution. Received this instruction from Dometic directly.
The fan should come on, then compressor, when cooling is needed. All previous RVs and homes had the fan come on when needed, not on all the time. Seems like a huge wear on the fan and increased electric $$.

[StageCoachDriver]

My guess is an efficient A/C unit cooling a small space along with a very sensitive thermostat. Mine does the same thing unless it's really hot outside.

[georgiawalker]

Had this happen when we bought our 2016 Montana 3791RD. Our problem was with the ac in the living room. What had happened was that during installation at the manufacturer, a wire that apparently had something to do with the thermostat and that hangs down from the ac unit was pinched up between the ac unit and the opening. Just so happened that the end of the wire, I assume the "business end," hung outside the opening, on the roof, directly in front of the weep hole for condensation. Every time it got wet, the unit would cut off until it evaporated off. It sounded to me (and the repair guy) that whoever puts those ac units in wasn’t paying attention (or didn’t care). It cost me $250 to get it fixed (including the time it took to run down the problem), but it’s been fine ever since.

[cghsatx]

Originally Posted by John McLean

Why is it that the bedroom AC unit in our new 2019 HM331RL will come on, run for maybe a minute, shut off briefly, come back on, run for maybe a minute, shut off briefly, come back on for a longer period, shut off, come back on and then repeat the pattern over and over?

I had same problem on my 2019 3731. Besides just running on high or low all the time, you can try "rebooting" the thermostat. Info is available from Dometic. You hold down the up/down buttons while on the main screen but I dont recall for sure so check online or with Dometic. That worked for me for a while, then the same issue started again. Dometic sent 2 new thermostats so I could try that. I prefer to to use Auto but the units tend to not cool enough in the daytime heat so have to use high, and put on low at night if the noise bothers anyone. Like others, I get so frustrated with this RV I wish I never bought it but selling is too much of a cash loss. Just have to try to forget about all the $ paid for what I thought was top quality RV and learn to live with it and fix it.

[Snoopy]

Also sounds like your unite could be low on freon. Dometic just replaced our living room 15k unite for that reason. it would do the same thing you stated. Only cost us our rally money to find out. unite quit in Las Vegas on the way to the rally.

[Carguy1965]

I too am very curious on this one. We just took our brand new 3121RL on its shakedown trip over the 4th, Its back at the dealer for a bit of post trip fix it list stuff. Both ACs are on the list..


I am in the AC business so I experimented a lot with the stats. During the daytime it was quite hot so I left them on high fan and AC, not really an issue while we are up and about and they would be running for the most part anyway. Evening/night time is quite different. Like it to be a bit more quiet so I tried auto fan. Both units would go straight into a cycle on and off almost constant mode. Literally shut down and 5 to 10 seconds later come right back on. Trying to sleep it drove us crazy. Ended up just switching back to low fan and leaving it there. Had a detailed talk with the service manager and they promise to fix it. None of our previous campers have ever done that, our trusty Rockwood would satisfy the call, shut off and stay off till the next time needed. Very aggravating and not what I was expecting from the most expensive rig we have ever owned by far..

[allenclme]

We have a 2017 3820FK. The AC on this thing is the worst. There are several threads either here or in the Keystone Owners site with some fixes. CW replaced both of my thermostats under warranty twice and it didn't make a difference. I don't think there's really anything wrong with them. The issue on mine is low air flow because of the duct system. The air blows plenty cold, 20-25 degrees cooler than the inside temp, there's just not enough volume on a hot day to get the coach cool. Have no idea how they say this thing is good up to 100 degrees.

[fuquatj]

allenclme....I have a 2017 3921FB, and have fought the same issue since purchase. Even had the 3rd A/C installed and wired so I can run all 3 at the same time. We were still wiping sweat when inside the camper if the outside temp was 85+. My dealer has tried to correct this over and over. Finally, last month they decided that the front A/C unit was starving for air due to the air intake ducts being mashed flat due to the curvature of the ceiling. They installed the old type A/C intake-output register directly under the unit. in the front bedroom A/C (on your model that's probable the kitchen A/C). It's noisy as heck, but for the first time in 2 1/2 years of owning this camper, it is actually cool inside.

Also, I assume that your 3820FK has the windshield, as does mine. That thing is good for nothing except functioning as a magnifying glass for the sun. I would never purchase a camper with the windsheild again.

[allenclme]

Yeah, we have the windshield. I got a big sun shade that's reflective just like for a car, and we leave that in when the sun is shining that direction. That made a big difference. Gonna pull out all of the diffusers and open them up because if you look at them, they restrict more than half of the duct area. Just haven't figured out how to modify them yet. Also in the Keystone site thread, there were some discussions about the intakes not having enough opening to meet dometic's installation specifications. I am really trying to figure out how Keystone sells this as being able to be lived in year round up to 100 degrees outside temp. Even at 90 outside, best we can do is 85 inside if in full sun.

[Al & Sheila]

So if I understand this correctly the AC cycling issue is the result of freeze up due to low air flow? And the remedy is to run the fans manually on high speed to improve air flow? Seems to me that Keystone should help out some way with recommending some type of fix either to improve air flow with return vent modifications or larger fan or discharge vents. They say these are four season living RV's with extra insulation, etc so summer living has to be listening to fans?

[DebNJim B]

I've heard some had little or no air flow in the ceiling vent as the ductwork had collapsed against the insulation and they put pvc pipe in to open up the ducts. Not sure how you get rigid pipe in there. Maybe they had flexible piping.

I have not had that issue and I run my fan on auto w/o problems.