The Operating Systems, Lower Level, Interior and Exterior Inspection sections are EXTREMELY condensed versions of those found in our home inspection book: Home Inspection Business From A to Z
Real Estate Appraisers are not required to be home inspectors. However, I will include these sections anyway to give you some basic details about home inspections.
Don't urn on any central or window or wall air-conditioning units when the outdoor air temperature is 65 degrees Fahrenheit or lower. The interior pressure that's required to properly operate an air-conditioning system is too low when the temperature is 65 degrees or lower. If the unit is turned on, there are a number of ways that you could damage the compressor or the other components and end up buying the owner a new air-conditioning system.
Don't listen to anyone that says you can test the system anyway when the temperature is too cold. Let them turn on the system so if it blows, then they have to pay for it. I've heard a few war stories about poorly trained home inspectors that turned on A/C systems in the winter time and ended up blowing the compressors. Don't let this happen to you.
Check the exterior compressor unit while the air-conditioning system is on. See if it's making any unusual noises or if it's very old and rusty. Check the data plate to try to figure out the age and size of the unit. The life expectancy of a compressor is about 10 years depending upon the amount of usage. The life expectancy also depends on the quality of the unit and the maintenance given to the system over the years.