By Dave Solberg
Dear Dave,
My air conditioner is working and blowing cold air but can’t keep up with outside temperatures. Both compressors seem to be working. I just had the Freon checked and that’s good. We are camping now, and the outside temperature got to 89 and the thermostat in the camper said 86. The unit didn’t turn off all day until about 10 at night, when the outside temperature dropped. I’ve also changed filters and cleaned the condenser. Any suggestions? —Tim, 2006 Winnebago Adventurer 37
Dear Tim,
Your Adventurer has a basement-mounted central air conditioning system, called True Air, which Coleman designed for Winnebago. It is basically two compressors packaged into a residential-style unit, typically on the passenger side at the back.
The unit actually ran 25 percent more efficiently than traditional roof air conditioners. However, it was not received well in the market as it took up valuable storage space, especially when designed in a diesel pusher. The engine took up the entire back end and the True Air took up a large compartment in the middle of the rig. The plenum had to be placed inside the living area. It also was noisy in the bedroom if it ran at night. [From Merriam-Webster: plenum: an air-filled space in a structure, especially one that receives air from a blower for distribution (as in a ventilation system).]
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My first question is, how did you check the Freon? All RV air conditioners have a closed system with copper piping that is pinched off and soldered with silver. There are no ports like in automotive or residential models, so it cannot be “charged” or checked with gauges.
Check the air conditioner filter
The filter for this is typically under the bed pedestal. The first thing I would recommend is to make sure you have the correct filter. Using a residential-style filter could cause air restriction and affect performance.
Below is the location of the filter and sizes. Note that the filter cannot be thicker than one inch and is made of lightweight fiberglass. Do not use the “lifetime”-type filters that can be washed as they will restrict airflow. Also, make sure there is nothing blocking the filter and the air return vent in the base of the bed pedestal. Make sure the door is open to draw air from the front of the rig. I have found that adding a floor fan in the bathroom helps move air more efficiently.
You also stated that you cleaned the condenser, which is accessible from the outside of the rig by lifting up the panel. This is a good first step; however, the evaporator coil is just as important and is harder to get at.
A detailed look at the air conditioner
Here is an exploded view of the unit (click on image to enlarge). You will see the evaporator coil is #13. You should be able to access it through the opening of the filter area and vacuum it.
The next step would be to get an airflow and temperature gauge called an anemometer, which you can get on Amazon here.
This will give you the exact temperature of the air going into the return air and air coming out of the vents. The system should be able to reduce temperature by 16 degrees. If it is not, then it is not working as designed. If it is, you might have poor airflow, which the meter will also determine. Then it would be time to have a technician check the amp draw and motor of the air conditioner.
Check the air delivery system (plenum)
One last thing that I got from my Airxcel contact is check the air delivery system which is called a plenum that comes out of the unit underneath and goes up through the back wall of your unit. This plenum has several connections that could have separated and the cool air is leaking out into the back cap. Get a flashlight and look up behind the fiberglass back cap and you should see the plenum coming out of the unit and going up between the cap and the back wall. If there are any gaps, the cool air will escape and not get to the inside.
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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If he paid someone to “check” the refrigerant he is owed a refund.
RV Air conditioners are not very efficient and noisy too. I am seriously thinking on how to install split-systems into my coach if the rooftops fail. They are far more efficient and quiet too.
I installed on on the 5th wheel. Whisper quiet 25 decibels and half the energy usage for the same BTU’s. That and it added a heat pump.
Thank you, Dave! 🙂 Interesting system. I can see benefits — fewer holes in the roof, ground-level for maintenance. I saw a Winnebago with this system while tailgating at a football game in 2017 of 2018. In that setting almost no negatives because storage less important for a short, weekend trip. I wonder if the system can be made smaller now (~20 years later) and made an option? I think some bus conversions have this sort of system, or recently did. Thanks again, have a great day, safe travels, and safe stays! 🙂
Or it could simply be a faulty AC unit. Our 2024 Coachmen Catalina has two (cheap) GE AC units. The main one puts out air at 70 degrees with air pulled it at 74 degrees The bedroom AC drops the temperature to 47 degrees.
Hacks we used for years when traveling in our motor home:
A) Try to park facing north or east and avoid west and south. I get it…not always possible.
B) Get and use an external windshield sun screen. We used a MagneShade (https://magneshade.com) and found that this shade really cut down on the amount of heat caused by sunlight while maintaining visibility.
C) Floor fans: We used two small floor fans to move air around. We placed one up front pointing to the rear and the other in the rear pointing to the front.
D) Window awnings over every window.
I have this marvelous system in my 1994 Winnebago Vectra 34′. It is located on street side just fwd of center. While it takes compartment space – it is well worth the loss! (The MH is weight compromised anyway!) It is, right now 97.1 degrees in the MH so I will be using it tonite. Also, the MH is designed for 50 amp, however, I am only connected to 30 amp, so have never used the twin compressors. With regard to the plastic plenum – I finally found where the mice were getting in – the plenum had separated, about 3/4″ from the unit. I use a standard home 14 x 20 fiberglass filter, it is under the couch. I love it and have been highly impressed with it – quiet, ducted air flow and effective.