Customer called due to no cold air blowing through the system. It is a Coleman, model number: TC4B6021SA, serial number: W1N8419823. Went downstairs to the unit, saw it running. Went outside to the condenser, saw it running. Hooked my gauges up and found the unit to be low on refrigerant. Added 3 pounds of 410a refrigerant to the system. Also added half a dye stick free of charge per RC. Let the system run for awhile. Pressures were good and got a temp split of 19°. Checked the evaporator for any freezing. Checked the pump to make sure it was pumping out properly. Took amp draws of the fan and compressor. Both running within manufacture’s specs. Checked filter, still good. System is running properly at this time. Will schedule a follow up to perform a leak inspection free of charge per RC. Add 3 pounds of 410a to help system run.