What furnace short cycling looks like
The thermostat calls for heat, the furnace starts, then it stops after a short run. It may try again several times, blow cool air, or never warm the house enough to satisfy the thermostat.
Homeowner Guide
Furnace starts and stops too often? Track what happens before it quits.
Short cycling means the furnace starts, runs briefly, then shuts back down before the home is warm. Do not guess at a part. The useful first step is noticing whether the burners light, the blower runs, the filter is restricted, or the system shows a safety warning.
Why the pattern matters
Short cycling can point to airflow restriction, a dirty filter, blocked returns, thermostat setup, ignition trouble, flame-sensing issues, blower behavior, or a safety limit shutting the system down. The $95 Springfield Diagnostichelps separate the symptom from the repair. Nearby towns may cost more.
Read the diagnostic pageKnow when to stop testing
You can check the thermostat mode, filter condition, and whether vents and returns are open. If you smell gas, leave the area and contact the gas utility or emergency services. If you see smoke, arcing, a hot electrical smell, or a breaker trips again, shut the system off and stop resetting it.