First-time user. Thanks in advance for your help. I have two 20-year old Rheem AC units outside (Classic X RAKA-030JAZ); one for the upstairs and one for the downstairs. They worked fine this Spring up until last week when at night it was a hot and humid 90 degree evening. That's when they both began to blow warm air. I shut them down for the night and checked them the next day. When I opened them up, I noticed that all three sides of the condenser coils on both units were heavily covered in thick dust from top to bottom, similar to what you'd find in a clothes dryer lint trap screen. Because of their thickness, like a sheet of felt, I was able to gently "peel off" the dirt. After doing so, I gently hosed them down from the inside out. They were spotless. When I turned the units back on, the upstairs unit cooled fine, while the downstairs unit wouldn't cool below 73 degrees, despite setting the thermostat to 68 and running it for 4 hours. I shut it back off. I'm guessing that the refrigerant is fine because the insulated copper pipes coming from the outdoor units to the house, and the insulated pipe running from the furnace from the evaporator coil area, are both very cold. I also changed out the air filters. There is no ice buildup anywhere. There is no rattling, banging, clanking, screeching, squealing, clicking, humming or hissing sounds. And the outdoor units are spaced out and not being blocked by any shrubs, etc. So, I'm wondering what I can check next. Reading online, it said to look at the capacitor in the outdoor unit to see if it's "bulging" and to see if the compressor is actually turning on, and to check the contactor. Is this valid? I am getting cool air, but just not cool enough. If the capacitor, compressor or contactor were bad, I wouldn't be getting any cool air, right? If it is valid to check these parts to see if they are working properly, how best can I do so, especially if the capacitor isn't visibly bulging? What tools would I need to perform these checks, and is there a step-by-step guide to wealk me through? Although I can manage to fix some things here and there, I am not an HVAC specialist nor do I have the unique tools. So, if I need to buy anything, I'd prefer a recommendation on the least expensive, yet effective, tools. Thanks for your help!!

Hello Everyone, I reduced the temperature at thermostat to Cool (50 Deg F), Thermostat clicked and furnace is running, air blow out in vents but external AC unit is not working, I checked at connector there is no power/voltage in wires coming from inside. Checked at the main electrical panel board and voltage is there at AC switch. Could you please help in troubleshooting this issue. Thanks in advance.