Performed a 2 system maintenance on 2 1 year old systems. Both systems are sealed well, ductwork is good, Drains are good. The downstairs system was frozen inside at the suction line and coil. I left with the system still thawing. I couldn’t get a read on the gauges for the downstairs system because of the frozen coil. I cleaned condensers tested amperage and MFD. everything is good except for the frozen coil. I believe it’s due to dirty filters that were changed right before I arrived. The upstairs system now has a 18 degree split and I added 2 lbs of R410A. I told the customer to wait a few more hours until the coil thaws and then we can see if the system cools properly.