When your RV AC freezes over it is never good. At Georgia RV Inspection and Repair we have seen our share of these, and have had the, not so fun, experience of it happening on our own units. Luckily those issues don't happen very often. Typically freezing issues are born from air flow problems. Much like the one in the photo here. The coils here rely on the heat from the return the room it is pulling from to prevent ice from forming on the coils. When you see ice forming on your coils you will often be faced with a situation where one of the following issues are taking place.
Dirty evaporator and/or condenser coils
bad flow dividers
dirty air filters
low refrigerant (not no refrigerant)
AC maintenance is one of the best things you can do to prolong the life of your AC unit, and ensure proper air flow. These things can get clogged easily by all kinds of things flying in the air. When coils get clogged it will raise the amperage sometimes causing the neutral wire to get hot and burn, or trip a breaker.
Flow dividers prevent hot air and cold air from mixing. If the dividers are not installed properly this will allow cold air to be mixed with hot air which will eventually cause the coils to freeze. Sometimes simple duct tape can help in sealing areas where the dividers are allowing the hot and cold air to mix.
Another issue can be high humidity. High humidity becomes a problem because the AC unit can not move enough air and pull the moisture fast enough to have the unit run efficiently. Sometimes a simple fix for this is to run your fan on low speed.
Low refrigerant can sometimes become an issue. When this happens the unit will freeze quickly. If your unit freezes with in a 5 or 10 minutes this could very well be your issue.
AC units today are closed systems, meaning you can't recharge them. You may be able to call a HVAC guy who can open the system and install a charge port, but the manufacture makes these closed systems for a reason.
Sometimes your unit freezes because of the thermostat. By thermostat I don't mean the one on your wall so much as the white wire in your coils that tells the system the coils are getting cold and needs to turn the compressor off. Testing this requires a multi-meter and a cup of water which allows you to test the ohms to verify the thermostat is actually working properly.
Many of these things can be avoided by performing maintenance. Maintenance is your best line of defense in prolonging the life of your AC unit. Fan combing, cleaning coils, and testing your electrical can go a long way in making sure your AC does not go out when you are camping on a hot day. While calling a mobile service tech is a great way to solve difficult issues, the steps above are simple and can often help quickly fix a simple AC issue.