The switch was faulty and the thermostat wiring was tangled
I tried to do everything I could to help my furnace when it began running inefficiently. I started noticing how often the furnace was running and how difficult it was to heat my home evenly. Before calling an HVAC professional, I tried replacing the air filter to see if that would help. The old air filter was covered in dust and debri, so I felt confident that the clean air filter I was replacing it with would do the trick. However, even though the clean air filter probably helped a little, I didn’t notice a significant change in the frequency my furnace was running. Next, I checked the outside unit to see if there were any branches or tall grass covering it. I cleared a few sticks and trimmed the bushes back, but I still didn’t notice a difference in my furnace efficiency. I broke down and hired an HVAC professional because I knew I’d done what I could to get my furnace running normally again. The HVAC professional was kind and considerate and he was really impressed with me for replacing the air filter and clearing the outside unit. Unfortunately, the real issue was the fan limit switch. The switch was faulty and the thermostat wiring was tangled. I was worried about the cost to repair the limit switch, but the HVAC professional said it was very inexpensive. I’m glad I did what I could before calling an HVAC professional, and I’m glad the situation wasn’t worse than it was.