Describe a full cycle
Note approximately how long the furnace runs and whether the room reaches the thermostat setting. Keep supply and return grilles clear and follow the manufacturer’s filter guidance.
Ask for the underlying cause
A technician should investigate why the cycle ends. Replacing a thermostat or a furnace without a diagnosis may leave the original problem unresolved.
Take this question into the conversation
“What did you find, what will the proposed work solve, and how will we know it worked?”
This is general educational guidance, not an assessment of your equipment. A qualified contractor must evaluate the actual system.