ac freezing up

A couple things. If the air inside the RV is humid, say, from a shower, the condensation can build on the fins and freeze up. While taking a shower, use the exhaust fan to vent humid air outside.
Use the high fan setting if you have one and use the on setting instead of auto so the fan is blowing constantly, instead of turning off when the compressor stops. This constant flow of air will help keep the fins from freezing up.

ok thxs but we havent took a shower and its the lines that are freezing i did have it on auto could the fins need cleaned the 1 i can see looks clean

The #1 reason any A/C freezes up is low on freon. I bet that is your problem.

if it is low on freon it wouldn't blow cold air would it

It could be cold if the charge is slightly off but as system cools it could very well freeze up. Also what is the temp in camper when it starting freezing up?

james1551 wrote:
if it is low on freon it wouldn't blow cold air would it

Apparently James 1551 has no air conditioning experience if he doesn't believe low Freon causes freeze up. Make sure you have good air flow through you evaporator coils. That can cause freezing also .

Run your fan on HI and see what it does.

May need the coil cleaned so that it gets enough air. My home geothermal unit had some freeze up's when I returned from 2 weeks with system shut off. If you shut the AC off and run the fan on high until it defrosts and try it again. After it had taken most of the moisture out of the house worked fine.

What 'lines' are you referring to that are freezing up?

If it has a wall thermostat it should have a freeze sensor. Very common for the sensor to fall away from the evaporator due to poor installation. Need to get up inside and check/reposition the freeze sensor. Remove all interior trim for access. Sensor needs to be direct on or in the evaporator coil fins.

While you are there check the plenum divider is properly installed. Again the divider is often poorly installed and will allow chilled air to immediately return to the intake plenum. Reposition and seal with metal foil tape from your local hardware store. See example here: http://forums.woodalls.com/index.cfm/fuseaction/thread/tid/28955299.cfm