Came out today for a leaking furnace. Upon inspection I found that the air filter was installed incorrectly. I replaced the air filter, checked the drain line and drain pan. The temperature split is was at a 13. I connected my gauges and noticed that the system was low on refrigerant. I added 2 lbs of nu-22 and now the temperature split is at a 19. This is an old amana system. My recommendation is to replace the system due to its age. The system is extremely loud at the furnace and the condenser is rusted through. I expressed my concerns about the age of the system and the homeowner declined to get an estimate for a new one.