Short cycling means the furnace fires up, runs a few minutes, and shuts down before the house is warm — over and over. It wears parts out fast and wastes energy.
1. Clogged filter
Restricted airflow overheats the heat exchanger and trips the high-limit switch. Replace the filter.
2. Dirty flame sensor
The furnace lights, can't sense flame, and shuts off in seconds. Cleaning the sensor is a common
furnace repair.
3. Faulty limit switch
A worn switch trips too early.
4. Blocked vent or flue
Pressure switch problems shut the furnace down for safety.
5. Thermostat location
A thermostat near a supply vent satisfies too quickly.
6. Oversized furnace
Too much furnace heats the air too fast. Only replacement fixes this one. If your furnace keeps cycling, schedule
heating repair before a cold night.
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