If anyone can help, I'd be very grateful. I am a widowed senior on social security and am at my wits end. I've lived in a fourth floor condo for four years and my AC is under warranty. The problem: The AC seems to run constantly, but can not seem to reach the "set" temp on the thermostat especially on very hot days. It is a HW/HWC Series Magic-Pak Through the Wall Unit by Lennox. Right now it is 90 degrees outside, my thermostat is set for 75 degrees and the inside temp of my condo is 78 degrees. On very hot days, the temp inside can go as high as 82 degrees. It has even tripped the circuit breaker a number of times. I've had the AC guy out as well as an electrician. The electrician says the problem is not electrical and the AC guy can't seem to find the problem although he has been diligent in his efforts. I am so frustrated... and the forecast for Friday is 103 degrees! Any thoughts or ideas? Please help!

It sounds like the A/C unit is not large enough to handle the cooling load. It is very common for people to undersize A/C units. You don't say the size of the room you are trying to cool. Rule of thumb is 5000 BTU for every 10x14 room. The heat load in a 4th floor condo would be pretty great so the unit is more than likely undesized.

It probably worked fine until it hit 100. Very common question asked here but only in summer. Your unit is probably working fine but does not have enough BTU to overcome the ambient load. Does it work better at night and when the temp is 90?