I'm not sure what you can do with the information but here's some possible explainations.

One or more supplies and/or return vents have developed leaks. The same vents might have become obstructed. Covers/grills for same vents are closed or covered. Evap coils have become clogged resulting in less air volume delivery. The unit may be worn and struggling. This is one you can kinda predict witout tools or training. Watch outdoor unit to see if it cycles off for at least a few minutes ever hour or less. A large tree died at sunny side of building. Drapes with lesser insulating quility were installed. A laundry dryer is venting into wall or attic. The unit next door shareing a wall with yours is vacant or otherwised different than past years. Ta-da,maintenance people are known to be inept. Eliminate all those with some degree of certainty and I will give you another batch. ^_^

"Maintenance Says: It's normal."

If you are renting, these are keywords that tell you to start saving up for your next place and plan your next move.

If you're not renting, find another HVAC company that is willing to give you a solution. On the flip end of that: solutions cost money... because solutions are what separate the men from the pretenders in this industry.

You may not like what I put here, but I think you came here for insight. If you're the home owner it will come down to how much playing around you're willing to do. Solution providers aren't in the business to 'play around'.

Be Careful: Some masquerade as solution providers and are not. That is the catch if there ever was one. This requires you to do some homework.

Air Conditioning Tips

very typical about upstairs level of 2 story condo being hotter than the lower, main floor level. You do not provide the living area size of each level. Your location? Outdoor temp when the condition occurs? Assuming your system is sized and operating correctly, you have very little practical options available to improve. Your situation is most likely due to poor ductwork sizing/design to the upstairs. You have adequate return(s) for upstairs? Ductwork to upstairs is accessible for modification? Insulation in attic has been examined for upgrade? Those would be the areas I would look at. You might consider a window unit for upstairs. And if you have money to spend, perhaps a small mini split system. Wish I could offer more options but there is not an easy or inexpensive fix. I hate to say this but it is true. Ductwork sizing and best design practices are the most overlooked area in the residential market. Getting better but still a long way to go.

IMO

"Maintenance says its normal, but it's not normally like this and I was here during the hottest summer on record."

It is not normal to have a 10 degree difference between the first and second floors. You may get 2-3 degrees difference on the hottest days of the year but more than that is not acceptable in my opinion.

It sounds like this problem did not occur in the past. Have any changes been made recently? Any renovations done to your townhouse or anything that could affect how the AC performs?

Are the registers for the second floor in the ceiling? If they are then the duct work feeding the registers are in the attic. It is possible flexible duct work may have become disconnected or developed a large leak. Someone needs to go into the attic and to a visual inspection of all the duct work and make the necessary repairs.

He said it worked fine for 11 years. That doesn't sound like a desighn problem.

for above poster...one usually sizes for the average summer temps...not extremes...while OP's location is not known, temps in my SE area yesterday were 100+, Certainly not the normal or average...I agree his ductwork should be checked and an overall PM performed to check both Delta T and supply temps both upstairs and downstairs along with refrigerant charge...wonder when the last PM was performed by a qualified dealer?..I would think the thermostat is located on lower level...who exactly is maintenance?...that may be part of your problem...

IMO

Robert, sounds like we're neighbors. I live in a 2 story condo and the upstairs is always hotter. We have 100 units & everyone has the same complaint. Even with central AC, some people still put a window AC upstairs.

This development is 30 years old and was built as cheaply as the city contractors would allow. I'm sure my ductwork is to blame because in the back bedroom upstairs (furthest away from the AC) I get barely a little poof of cold air. I also would benefit from that spray foam blow-in insulation. But that & the ductwork would cost a fortune & my condo isn't worth it.

Luckilly I'm not dealing with the ductwork issue this summer. My central AC died and I purchased an inexpensive window unit for upstairs & downstairs. Now the temps are perfect. Sadly it was cheaper to buy 2 window units versus fixing the central AC. Maybe I'll save up & replace it next year.