Saturday, December 9, 2023


Should I run the RV roof air conditioners when I am not using the RV?

Dear Dave,
We are seasonal in Hudson, Florida, November to May, but we use the RV January to May. Is it best to leave the air conditioners on when we are gone? Is it best to pull down the blackout shades or the light filtering ones? You have probably answered these before. I try to read RV Travel every day but might miss a day once in a while. Thank you. —Jim, 2016 Cedar Creek Cottage 40CCK Hathaway Edition

Dear Jim,
I would not suggest leaving the roof air conditioners running while you are gone for even a few days, let alone June through December. Florida gets extremely hot and humid in the summer and fall and your roof air conditioners most likely will be running close to maximum capacity.

Since it is a 2016, I doubt they have any type of hard start product installed such as SoftStartRV, so when each unit comes on, it will have a very high amp draw of almost 45 amps for a brief second. You did not state what shoreline power you are plugging into. However, even if it is 50 amps, the roof air conditioners running all the time can be a stress on the power outlet, cord, and your distribution center.

The roof air conditioners running most of the time is just too much risk of a short or other electrical issue. Plus, it would put a lot of stress on the compressor and fan motor of your units. I realize some full-timers would have their units running most of the time; however, the life expectancy of the A/Cs is greatly decreased.

What you can do instead of using roof air conditioners

Since you most likely will be plugged in, I would recommend shutting off the roof air conditioners, open a couple of roof vents that have a MaxxAir cover, and using a small fan inside to exhaust hot air. You might want to look into a temperature sensing roof air vent as well that would temporarily turn on when temperatures get really high. You can find the Fan-Tastic model on Amazon here.

There are several models available with some that not only turn on at a certain temperature but some that also open the lid at the set temperature and close if it rains. However, if you have the MaxxAir cover, you can leave the vent open all the time.

Use a moisture absorption product

I would also suggest installing some type of moisture absorption product such as DampRid or the new version I have found called H2Out. These canisters absorb moisture in the small beads and are reusable. Just bake them in an oven for a period of time to dry out them out and place them back in. The only issue with both of these is you need to replenish the DampRid every couple of months, and dry out the H2Out about the same. You can find the product on Amazon here.

As for the shades, I would pull down the black-out curtains to help keep it cooler inside as well as keep the sun from fading the fabrics and window treatments.

 You might also enjoy this from Dave 

Are there any “good” alternatives to a traditional RV roof air conditioner?

Dear Dave,
What is a “good” alternative to an RV rooftop air conditioner? The more I look at it, the more confusing it gets. I should have added a second A/C when I ordered my current rig. I am open to any options! Thank you. —Randy, 2022 Flagstaff 8529RLS

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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.



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Neal Davis (@guest_256394)
1 month ago

Thank you, Dave. We set the thermostat high in the summer and low in the winter when our RV is in our RV barn rather than on a trip. Thus, our air conditioner units do run in the heat of the day to keep the inside temperature around 85° F. We also lower our blackout shades and the RV remains shielded from the sun except late in the day.

Tom Jones (@guest_256383)
1 month ago

It’s true that the FantasticVent fans (which I have) will turn off if it rains. But they won’t turn back on after that. So, that’s only a solution until the first rain. Also dew falling on the roof at night will shut them down. I can’t comment on whether vent covers will prevent this (“reliably”).

Steve Hericks (@guest_256253)
2 months ago

There is some ‘lore’ that says run A/C periodically that comes from automotive A/C units. ECU’s are timed to run A/C occasionally in the off-season in order to circulate oil to lubricate the rubber o-rings on the refrigerant connections but particularly the pump shaft seal. Doing so may be interpreted as a need for ALL A/C’s to operate this way but that is untrue. ONLY automotive A/C’s use o-ring seals and externally driven compressors that benefit from (but don’t necessarily require) lubrication. The RV rooftop units are a ‘package unit’ meaning all components are in one ‘package’, have only metal brazed connections throughout, and a completely sealed compressor.

Diane McGovern
2 months ago
Reply to  Steve Hericks

Thank you for your always knowledgeable and helpful information, Steve. Much appreciated!👍 Have a great day! 😀 –Diane at

Ray (@guest_256220)
2 months ago

Addressing moisture buildup, we store our RV plugged in and completely enclosed. We run 2 desktop dehumidifiers. These definitely remove more water than the cannister style of dehumidifiers. However, they tend to fill up and stop every 2 weeks or so. Keeping the humidity down agrees with that voice in my head, so when I find their catch trays full, I wonder how long they’ve stopped working. Your article gave me an idea. If I trick their float cutoff switches, I can remove the catch trays and then set them in the sinks, thereby draining them into the gray tanks and keeping them working full time. Add a little antifreeze for the S traps mid-winter and this could work.

Tom Jones (@guest_256382)
1 month ago
Reply to  Ray

If you drain it into the sink, the gray tank will fill up and potentially overflow with catastrophic consequences. Unless you have a way to leave the gray tank open and aren’t worried about rats or mice, or you can screen it off (it will only be water coming out). Another thing you can do is connect a hose and let the dehumidifier run as much as needed without having to stop and empty the tank. If you have a battery compartment under the stairs, it is vented to the outside so you can run the hose out through that (sealing off as needed for mice and insects). Otherwise you may have to improvise a water drain outlet.

Jim Johnson (@guest_256189)
2 months ago

Hi Dave, this may be a silly question… We only have one roof vent (bathroom). We took the option to install a 2nd A/C unit in what was the bedroom vent. When we are in residence we can crack a window to supply make up air when we run the bathroom vent fan. But during the off-season (we still have shore power) when all the windows are closed, where does the make up air come from if forcibly exhausting hot air? I have deliberately sealed the trailer as tight as possible to prevent insect incursion. Last note, we do leave the vent open (under a hood) in the off-season to allow natural ventilation as a means to prevent moisture build-up.

David Solberg (@guest_256214)
2 months ago
Reply to  Jim Johnson

When you reference “make up air” I assume you are talking about how air gets into the rig to be exhausted so as to not create a vacuum? Trust me, as tightly sealed as you think your rig is, there are still many areas that air can come in such as seals around the slide rooms, windows, doors, etc.

David (@guest_256183)
2 months ago

Dave, it is also important to mention that running the air conditioner when the RV is not occupied wastes a lot of energy!

David Solberg (@guest_256215)
2 months ago
Reply to  David

Good point!

Leslie (@guest_256219)
2 months ago
Reply to  David

When we Glamp in the summertime in CA some places are above 100 F. If we were to turn off the AC while we were gone, for several hours exploring, it would take hours to cool everything down again. We do have it on ‘Auto’ and usually around 78, which will keep the trailer cooled down enough that everything doesn’t overheat again.

Maybe you’re meaning unoccupied for long periods of time.

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