[Deus Ex Verra]

So I bought this car in late June last year and other than this overheating its in great condition. Quick info:
92 Accord EX with stock engine (only parts that have been put on it are replacement OEM)
mileage: 134,000
Location: Kansas, USA (100+ degrees is normal in the summer here)

I had this same issue last summer and eventually had to replace the radiator and thermometer. While it did run hot (often above 3/4 on the temp gauge), things really only got bad when i ran the A/C. After the replacement the weather had cooled down and running the A/C was no longer required (or desired), but I did notice that it still ran pretty hot (generally at 2/3 or more). Now it's getting warm again and the car is running hotter and hotter and I really don't want to have to replace the radiator (again). I can go without A/C (but don't want to) and this isn't good on the engine. Any ideas?

Coolant is completely full. No leaks to my knowledge. The radiator replacement was NOT new but came out of an identical car and only had 30k miles on the radiator and no issues. The replacement install was professionally done and not overseen by me. I'd prefer to do this fix myself (want to learn how to work on cars) if possible. Sorry for the long post, just trying to provide as much detail as possible. Lastly, what damage or wear should I be looking for now and in the future in regards to this issue?