Performed ac maintenance. Homeowner wasn’t too sure on the equipment he had in his home. 2007 Amana Furnace 2 stage variable c width 2007 amana evap coil box txv d width 2018 Lennox ML14 5 ton r410a single stage 14seer. Homeowner purchased the home a few years ago. I believe the original outdoor unit was most likely a two stage unit based on indoor unit wiring. Y1 and y2. But before the homeowner bought this house the outdoor unit was replaced with the Lennox single stage. The indoor evap coil is busted. Oil present in the primary pan, oil present on the backside of coil elbows. Performed leak search due to the presence of oil and the low delta t. Only 13 degrees. Confirmed refrigerant leak with leak detector and soap bubbles. Filter needs to be replaced. He’ll order a new one. Equipment is turning off and on properly. Capacitor for condenser is within tolerance. Fan motor is running ok and so is the compressor. This system will struggle this summer due to the low refrigerant lev