Now that we have seen how an air conditioner does the work, let's look at the mechanics involved. We can see that there are two main systems in a roof top air conditioner, the sealed refrigeration system, and the air handling system. In addition to these systems, there is, of course, the control system (thermostat and fan switches).For the sealed system, all brands, Coleman, DuoTherm, Carrier, Intertherm, and others, work the same, using the basic principals of refrigeration. In the sealed system, the main component is the compressor- which, by itself, is not serviceable, but there are some components that are external to it which are serviceable. For now, let's look at the most common and easily repaired problems. The one major compromise that roof top air conditioners all have in common is the fact that they all have to route both the return and supply air through a standard 14" by 14" cutout in the roof. This is even more amazing when you realize that the average 13,500 btu air conditioner has just over 1 ton of cooling capacity- a 15,000 btu model is around 1 1/4 tons.

A motor home or large trailer that has two 15,000 btu air conditioners has 2 1/2 tons of air conditioning- or enough capacity for many houses. The two most common complaints are "Not cooling enough" and leaks. Let's look at "not cooling" first. Not blowing cold air. The first thing to determine is if the compressor is coming on. If it isn't, it is likely a control problem with the thermostat or relay board (if you have a wall mounted thermostat). If the compressor is coming on, then you need to look into the airflow of the unit. Whether or not the compressor is coming on, you need to check the voltage. Like every appliance on board, the air conditioner needs adequate power to operate. If the voltage is 110 volts a.c. or below, the effectiveness of the unit will start to suffer. After verifying correct voltage, we need to look at how the air conditioner does it's job- it requires adequate air flow over both the inside (evaporator) and outside (condenser) coils. If the air filter is clogged refrigerant will not be able to pick up enough heat from the inside air, and if the condenser coils are blocked by leaves, it will not be able to give off enough heat to the outside air.

Most RV rooftop air conditioners have washable filters, which can be vacuumed or rinsed off in a sink to clean. If you are in summer weather where the air conditioner is running 24 hours a day, the filters should really be at least vacuumed once a week. Note that if the filters have been neglected, the evaporator coils probably need cleaning as well. These can be seen when you remove the air filters, and possibly the inside air box. Likewise, the condenser coils can be seen after removing the upper shroud. Note that some air conditioners draw air in from the back, and some blow air out the back. You will need to determine which your is, or just check both sides of the condenser. An unavoidable drawback to being able to mount an air conditioner in a 14" by 14" roof vent cut out is that both the supply air and the return air are in very close proximity to each other. This can be a problem if the two are not sealed well from each other- if the cold supply air can recirculate into the return side, the evaporator coil can easily freeze up, plus that is cold air that is just going to waste.

Note that this is normally more of a problem with ducted type air conditioners than the standard exposed air box type, but it is something that you need to be aware of, in all cases.A fairly easy way to check is to simply, carefully put your hand into the return air duct and feel for cold air. air purifier warehouseIf you can feel cold air, you need to take care of the air leak.air purifier vs humidifier allergies The last problem we will talk about is heat gain. air knight purification system reviewsOne compromise that most RVs make is in the insulation department- after all, if they had 6" thick walls for good insulation, there wouldn't be much living room left, so.. In very hot weather, and direct sun, the amount of heat that the RV will pick up may be greater than the amount of heat the air conditioner will pump back out.

In this case, shade is the answer! Whether you use an awning, or an oak tree, in very hot weather, keeping the direct sun off of the RV will greatly increase your comfort.Roof Air Conditioner Water Leaks A fairly common complaint is that of water leaks from the rooftop air conditioner. These do not have to be nearly as hard to find or fix as people often make them- they simply need to be dealt with in a systematic method. The first question when dealing with this type of leak is- does it leak when it's raining or when the air conditioner is running (or, more rarely, both)? To deal with either, we need to look closely at how the air conditioner is mounted, and how it deals with the condensation generated while running. The main thing to keep in mind, is that the air conditioner is sealed to the roof using a sponge rubber gasket- this gasket is compressable, and really is a long term maintenance item (they can last years, but not forever). This gasket is compressed by 3 or 4 bolts running from the inside assembly up to the top.

For either "rain only" or "while A/C is running" leaks, first make certain there is at least 1/2 inch of gasket left (it is not tightened right down to the roof), then check the bolt for tightness- just make sure they are all snug, but don't over tighten- there must be the gap between the bottom of the A/C and the roof. The reason for this gap is that on most roof top A/C/ units, the condensation drains out the bottom of the unit- between the base of the air conditioner and the roof. For this reason, never, ever seal around the perimeter of the air conditioner- I cannot say how many times I have had to deal with a unit where someone slopped goop around the base of the air conditioner, trapping water in where it has to leak inside. The "inside"coils of the air conditioner sit in a drain pan, to collect the condensation, which then runs out a small hole in the side, and out the bottom. If the leak is both while raining, and while running, and the gasket is still thick enough and tight, odds are there is some roof deterioration underneath the air conditioner- as long as the roof isn't sagging, causing water to puddle up around the air conditioner, which can be checked by pulling a string across the roof, from side to side.

If there is significant sag, the air conditioner needs to be raised, either by installing 2 gaskets or by removing the air conditioner and putting shimmed between the roof material and roof frame- this is the method I usually use, building up with strips of 1/4" plywood, until the air conditioner is high enough that water cannot run in. Of course, roof sag may be an indication of a larger problem, but quite often it is just age, and other than a bit of sag, there are really no structural problems. If the leak is only while the unit is operating, first check all of the above, if everything checks out, odds are that the drain holes are simply plugged up, or that the evaporator coil is very dirty, which will cause enough suction to keep the water from draining properly. To deal with this, we have to get up on the roof, and do some disassembly. You have to remove the plastic shroud, and then the front evaporator cover, which is usually held on by a number of screws. This will get you in to the evaporator and drain pan- it is usually fairly obvious if the drains are clogged, and they are easily cleaned, but if you are going this far, it is a good time to check the evaporator coils for dirt, and clean them if needed (if they haven't been cleaned in a while, it really wouldn't hurt to clean them.

Coleman recommends "Formula 409" cleaner, which works well- I use "VoomRV", but most mild degreaser type cleaners should do fine. I don't like to use the standard coil cleaner products for this, as most of them are acidic, and while they would be fine in a large house air conditioner, I don't like the idea of these products running down the outside of an RV. Another great cleaner that I don't like for this application is "Simple Green"- it has some issues with aluminum. The hardest part of cleaning the coils is rinsing them off without flooding the inside of the RV- being very careful with the water, putting rags in the opening from the top, and putting down a protective cover inside should keep everything A-OK. While you are up there with all these items, cleaning the outside condenser coils is a great idea- on air conditioners only a few years old, I can usually lower the amperage draw by 1 to 2 amps, simply by cleaning these coils (letting them get rid of the heat more easily). So- understanding what kind of leak you have, and where the water is supposed to go in a properly operating system, we can see that solving roof air conditioner leaks really isn't a hard job, as long as you have a bit of knowledge.