Hi guys, Just joined now. I used to belong to Just Answer, but then got very busy and had to leave that. I am based in Brisbane running a small family business doing air conditioning and refrigeration. Well thats me. Cheers

I’m looking for some advice on a strange issue with my approximately 30-year-old central HVAC system. When I lower the thermostat by 1–2 degrees, the air conditioner will run continuously for a very long time before it finally reaches the new set temperature. For example, if I change the thermostat from 76°F to 75°F, it may eventually reach 75°F, but the AC keeps running even after the thermostat shows it has reached the set point. I’ve also noticed that the house feels much colder than the thermostat setting while it’s still running. The really confusing part is this: if I then raise the thermostat back up to 76°F, the AC immediately shuts off—even though the thermostat may now show the room temperature is 73°F. That doesn’t seem to make sense to me. Has anyone experienced something similar? What are the most likely things I should check or have inspected? Could this be a thermostat issue, a sensor problem, an airflow issue, or something else? The system is about 30 years old, but it still cools the house. I’m just trying to understand why it seems to overcool and why it won’t shut off until I manually increase the thermostat setting. Any advice or troubleshooting suggestions would be greatly appreciated. Thank you!