Tell them to leave the t-stat at 75 degrees when they go on vacation, and you won't have a problem. If your guage readings are perfect, then check the duct work. they may have a supply with a hole in it under the house.
Originally posted by tom2448
I put in a new ac in a house last summer. The ac has been working great all summer long keeping the house at 75 degrees. They called me tonight said they came home from vacation and turned on the ac it ran for 6 hours and did not drop below 82. My gauge readings are perfect it just doesn't seem like it is blowing that cool or strong out of the registers.