Air Conditioner Short Cycling

[Time2Go!]

Good morning!

We have a 2021 LE2 #743 that we picked up mid-February. Our first few trips we had no need for the A/C. We did turn it on after pick up to make sure it came on and cooled but didn't really run it for any amount of time with it being winter with snow on the ground in Tennessee.

Our past few trips when we have used it overnight and some during the day it short cycles (that's the term my husband used). The fan comes on runs 5 or so minutes then cuts off.  Five or so minutes later it does the same thing. About every 4th time the compressor will kick on for a few minutes and then right back off. It cools fine however it is impossible to sleep with the constant on and off cycling. Friends that we camped with this past weekend even asked us what was up with the constant cycling of the A/C. We were hooked up to shore power every time we have used the A/C.

Anyone have any ideas? It's the Dometic 11k A/C unit and is brand new.

Guess we'll start a ticket with service unless someone here has ideas on what could be wrong.

Thanks,

Cindy

[John E Davies]

There are so many possible reasons that the average owner won't be able to do much. I think you need to have an AC technician check everything, it may be low on refrigerant, have faulty wiring or control board, or perhaps the evaporator coils are icing up, if it is super humid outside. The latter can be solved by running on just fan for an hour so the ice can melt. Good luck.

John Davies

Spokane WA

[BackofBeyond]

A few things to consider:

What was the voltage displayed on the progressive readout before the unit cycled the fan, during the fan, and when the compressor tried to cycle.

Do you have the easy start?

RB

[Time2Go!]

We do have the easy start but we have only run the A/C while hooked to shore power. Does it still use the easy start then or only when on generator or invertor?

[topgun2]

20 minutes ago, Time2Go! said:

Does it still use the easy start then or only when on generator or invertor?

Yes the ac will use the Easy Start any time it powers up regardless of the source of power.

[Landrover]

Not sure if this will help your problem?  My Ac would cycle  often if it had been a hot day. I found when you first start your Ac open all you cabinet doors your pantry, closet and the bathroom door.  A lot of heat gets trapped in those areas. Once all that radiated heat  is removed the interior remains cooler. And the Ac unit didn’t cycle as often. In stead of every 5 mins it was 20-30 minutes. Worth a try. 

[Jim and Frances]

 

I totally agree with John E Davies comments - Googling " rv ac compressor starts then stops" is not reassuring!

I just happened on this on Keystone forum...maybe helps or worthless.

Then this in info I found on the Easy Start site about short-cycle prevention - maybe looking at the Easy Start display could be a clue?

Unfortunately, the list of potential issues (and links to things) is very long), like the above, or overheating, or ....

Good luck on finding the cause and solution!

[Lori L]

Hello. We just took delivery of our Elite II and are experiencing the same short cycling issue. Sometimes with as little as 2 minutes between cycles. I was wondering if you were able to resolve the issue and how?  
 

Thanks!!

[MobileJoy]

We noticed the same effect and opened a ticket on it. Unfortunately, we have no solution at this time. Jason recommended that we change the thermostat to a temp that is not close to the outside temp, and it should behave better. Since we have been sidelined from camping temporarily, we will not be able to get back to this for a couple of months. We will be watching this thread. In our case, the cycling without compressor turn-on can be as short as just a few seconds, starting at a couple of minutes and getting shorter each time until the compressor finally does turn on.

 

[johnwen]

On 6/2/2021 at 6:15 PM, Jim and Frances said:

 

I totally agree with John E Davies comments - Googling " rv ac compressor starts then stops" is not reassuring!

I just happened on this on Keystone forum...maybe helps or worthless.

Then this in info I found on the Easy Start site about short-cycle prevention - maybe looking at the Easy Start display could be a clue?

Unfortunately, the list of potential issues (and links to things) is very long), like the above, or overheating, or ....

Good luck on finding the cause and solution!

Hi  Jim and Frances.  The Keystone link provided me with refreshing, general troubleshooting ideas and was a synergistic post for the 1st  half of reading, then devolved as most do without resolution.  It helped me with my "little box" thinking.  The Easy Start pdf deserves a little more of my time when I experience my problem next time.  I would have never thought the Easy Start could have been a suspect as it has been working flawlessly for the past year in my Casita.  My transition to the Ollie next year is much anticipated and I actually welcome "some" challenges to keep me busy 🙂, ones that can be resolved, however!

Thanks,

John

[LCTraveler]

We picked up hull 836 this last June and experienced something like what you are describing. Jason did a 2021 walkthrough video that seems to be relevant on this subject. There is a quirk to how the AC works and Jason explained it this way. If you have the fan in auto with the AC on it will run the fan on high until getting close to set point and then switches the fan to low. As it makes this transition the fan shuts off for a short period of time before coming back on. This appears to be a short cycling condition but is actually not. I believe Jason suggested that you run the fan in manual low when running the AC . We mostly dry camp so don’t run the AC that much so haven’t had a chance to test this out. 
Mike

 

[Mike and Carol]

Whenever we run our AC we set the fan on low.  No cycling issues.  Mike

[Time2Go!]

We ended up using the manual low fan speed and it definitely helped. Also adjusting the temp up a degree or so from where it was set seemed to make a difference as well.  

[Piney Woods Ranch]

We're having the same issue and the frequent short fan starts and stops is not only annoying, it's aggravating as it might be a sign that something is wrong.

 

The downside of running in the "Low" setting the is that the fan NEVER shuts off - which makes it about impossible to watch TV, have a conversation without shouting, or even hold a thought in your head.

 

We have a marine A/C unit in a boat, and it regularly turns on the fan for a few seconds to "sniff" the air temperature to see if it needs to turn on the compressor. That is annoying. The situation in the Ollie is worse.

 

I doubt this condition is a power issue, as on initial start-up, the fan always starts and then the compressor kicks in. If it were a power issue (IMHO) the unit would certainly falter at that time.

 

Frankly, I think this is a bad programming job by the Dometic engineering people than can and needs to be fixed. Once they do that, then maybe they can reduce the noise level to something less than running a Harley in your camper...

 

 

 

 

 

[Steph and Dud B]

@Time2Go!, did you ever get a resolution to the short cycling? We're at the mothership now after our new LE2 was doing the same thing yesterday/last night. With the fan on continuous Low the compressor would run for 2 minutes, stop, then repeat after a 3-5 minute pause. Shore power was good, temps in the mid-80s/mid-70s. Dropped the thermostat setting to 68 with no change in the behavior. Thought maybe it froze up, so switched to High fan only - no A/C - but saw no drainage from the drain tubes, so don't think it was iced. Right now, OTT can't duplicate the issue in their shop. A mystery...

 

[Steph and Dud B]

Update: I think we've identified the problem. The short cycling returned the night after OTT inspected the unit. Immediately after a cycle shutdown I went to the thermostat and shut it down so I could see the current temperature it was reporting. As I watched, it rose 3 degrees in about 2 minutes. An IR thermometer verified the final reading was the actual temperature of the thermostat. Working hypothesis: the thermostat was ingesting cold air directly from the overhead A/C unit, causing an early shutdown. When the cold airflow stopped, the thermostat called for A/C again and the process repeated.

Experimental solution: the thermostat has vent openings top and bottom. I placed a folded handkerchief over the top vents to shield them from the cold airflow. Viola! Normal A/C operation for the first time! I was concerned maybe the thermostat needs the top vents to release internally created heat, but that doesn't seem to be the case (because that would cause increasing calls for A/C, which didn't happen).

The weather has cooled, so I can't field test anymore. Going to try something more elegant than a folded handkerchief next time. Maybe a piece of felt. I think our mystery is solved, but it raises other questions. Why couldn't Jason recreate it at Service? Why aren't more people reporting this issue?

[mossemi]

Some more of that Yankee Ingenuity.  You da man!

Mossey

[topgun2]

9 hours ago, mossemi said:

You da man!

or woman! 😁

[Steph and Dud B]

10 hours ago, topgun2 said:

or woman!

Man in this case, although Stephanie was the one who noticed it was still short cycling so she gets some credit, too.