A modern furnace runs a strict startup sequence, and knowing where the sequence breaks is most of the diagnosis. The thermostat calls, the inducer motor spins up to prove draft through a pressure switch, the hot surface igniter glows, the gas valve opens, the burners light, the flame sensor confirms fire, and only then does the blower deliver heat to the house. In Palo Alto, CA, the failures cluster at predictable points: an oxide-coated flame sensor, a hot surface igniter cracked from years of thermal cycling, a pressure switch that will not close because the inducer is weak or the condensate trap on a high-efficiency model has clogged, or a control board with a burned relay. Each one stops the sequence cold, and each one mimics the others from the hallway.
When the AC quits in summer, see AC Repair.
Signs You Need Furnace Repair in Palo Alto
Recognizing the warning signs early can save you time and money. Here are the most common indicators that it's time to call a professional:
- Water, rust stains, or black soot around the flue or cabinet
- Loud booms at startup caused by delayed ignition
- Yellow, wavering burner flames where they should be sharp blue
- Flames that start, last a few seconds, and go out again and again
- The furnace clicks and glows but the burners never light
- Air moving through the vents that never gets warm
- Frequent on-off cycling that never reaches the thermostat setting
- Squeals, scrapes, or grinding noises behind the blower door
Early Action Saves Money
What seems like a minor issue today can take out a compressor or heat exchanger tomorrow. If you notice any of these signs, call (650) 220-0821 for a prompt inspection.
