SusieandDon

We have a 2002 29ft HiLo, it was used but in excellent cond. I have a question about the a/c someone may help me with. It cools wel,l but it freezes up sometimes, the filter is clea., I asked a rv serviceman about it because I was told it may need freon, but he told me the a/c system was sealed and there was no way to add freon. Is this true about a sealed system?