If you are referring to Hilton Head, KHXD, then the difficulties are possibly due to it being an AWOS and not ASOS. AWOS are antiquated systems that can be put at lower priority airports. If I recall correctly, AWOS do not have a mandate to be augmented by humans, not do they require an alternate power source. Therefore, if there is a commercial power loss the system just goes dark. We simply do not fund our environmental observation networks in the US and the truly upsetting part is that it would not cost too much money to do so.