# Furnace Symptom Guide (Demonstration)

Canonical page: https://denverfurnacerepair.com/guides/furnace-symptoms
Demonstration content by VisibilityReady / Fat Wallet Internet Marketing. Not an operating business. Educational only; cannot diagnose a specific system.

- No heat at all: thermostat, power, tripped safety, ignition, or flame sensing. Check thermostat, breaker, switch, filter, panel door. Call if it locks out again after one reset.
- Blows cold air: burners not lighting, fan set to ON, or overheating lockout. Set fan to AUTO, replace loaded filter.
- Short cycling: restricted airflow, dirty flame sensor, oversizing, thermostat placement.
- Some rooms always cold: duct design or leakage, dampers, single-stage equipment, insulation gaps.
- Higher gas bills: dirty burners, restricted airflow, thermostat, aging equipment, weather.
- Banging at start: delayed ignition. Call promptly; do not adjust gas components.
- Squealing or grinding: blower or inducer motor wear.
- Burning dust smell on first use: normal if it fades within hours.
- Rotten egg or gas odor: leave the home; call 911 or the gas utility from outside.
- CO alarm sounding: get everyone outside; call 911.
- Water around furnace: blocked condensate drain, humidifier or AC coil drain.
- Yellow or lazy flames: incomplete combustion; inspection needed.