I went on a service call last week, in a nicer gated community home in my area. The homeowner informed me that they had 3-4 other techs out over the years, and they still felt their upstairs AC isn't working properly.
When I arrived I found the unit to be low on charge, and a schrader cap was missing. I began to charge the unit up and started to end up with 60psi on the low and 240 on the high. 15 year old unit, 85 ambient 76 in the house, 4 ton.
I suspected a airflow problem, and when I went up into the attic, I found that some knucklehead had installed a 4 ton upflow furnace and coil, but didn't have room for a plenum so they simple cut 4 ducts off the evaporator coil casing itself. (Even I didn't notice it at first, because its not something I have ever found missing before)
I tried to find some research online to help explain to this gentlman why his system will not run properly until this problem is addressed, also how its costing him alot more in electricy and shorting the life span of his unit. Any advice would be appreciated.