Reading outlet voltage

Okay a little recap I went to town today and the only surge protector they have was for over voltage which is Not a problem. LOL! Anyways I did pick up some a/c coil cleaner to and elec. grease for all contacts. Cleaned all wiring contacts. Cleaned a/c unit. has worked fine so far. also put meter on pole instead of inside camper. With everything cut off including the converter unwired I'm only pulling 118v But the weird thing at idle it floats from 118-115 so it has to be a combo of low voltage dirty ac and air temp sensor on coils. After one at a time loading it back up with all appliances It still hasn't dropped below 113.5. So now I'm just waiting for all campers to return from pool to see what might happen to voltage. Think I'm going to have to break down and buy a transformer for security. Do not want this crazy thing to act up if we run to pool with pups in camper.